Lithium ion battery cathode material, preparation method and application thereof

Abstract

The application provides a lithium ion battery positive electrode material and a preparation method and application thereof, and belongs to the technical field of electrode materials. The lithium ion battery positive electrode material provided by the application has a structure as shown in general formula (I): in formula (I), n is an integer of 3-10, and X is one of O, S, C(CH3)2 or NCH3. The organic small molecular compound formed by connecting two diphenylhexa-membered rings through an alkyl chain is used as the lithium ion battery positive electrode material, the organic small molecular compound has a high redox voltage of more than 3.4 V, and is favorable for improving the energy density of the battery; the crystallization performance of the molecule is adjusted through the flexible alkyl chain in the middle, so that the positive electrode material is more uniformly dispersed on the electrode surface, which is favorable for the exertion of the electrochemical performance, and improves the structural stability, cycle performance and rate performance of the lithium ion battery positive electrode material.

Description

Technical Field

[0001] This invention relates to the field of electrode materials technology, and more specifically, to a lithium-ion battery cathode material, its preparation method, and its application. Background Technology

[0002] Efficient energy storage systems are crucial for portable electronic devices, electric vehicles, and smart grids. Lithium-ion batteries, as one of the most viable energy storage technologies, have experienced rapid development over the past few decades. From a compositional perspective, the cathode material is the most critical factor determining the performance and cost of a lithium-ion battery. Among the many types of cathode materials, inorganic cathode materials such as LiCoO2, LiFePO4, and LiNi... x Mn y Co 1-x-y O2 and other materials are most widely used. However, over time, the scarcity of lithium, nickel, and cobalt resources will further intensify, and heavy metals will continue to harm the ecological environment. At the same time, although lithium-sulfur batteries utilize abundant and readily available sulfur as the cathode material, their average voltage is low, around 2.15V, and their cycle stability and rate performance are not ideal.

[0003] As an alternative, organic electrode materials composed of renewable elements such as C, H, N, O, and S are not only green and sustainable, but their chemical structures can also be customized to enhance electrochemical performance. Among these, carbonyl compounds with high specific capacity and nitroxide radical polymers with excellent rate performance have been extensively studied, but their discharge plateau voltages are mostly below 3.0V, limiting further increases in energy density. Meanwhile, organic compounds with high discharge plateau voltages often suffer from poor structural stability, cycling performance, and rate performance. Summary of the Invention

[0004] To address the aforementioned problems, the main objective of this invention is to provide a lithium-ion battery cathode material, its preparation method, and its applications. This invention uses two dibenzo-6-membered ring structural units as electrochemical redox centers. During charging, electrons from the nitrogen atoms in the dibenzo-6-membered ring structural units are eliminated from their HOMO orbitals, resulting in a high redox voltage exceeding 3.4V. The two dibenzo-6-membered ring structural units are connected by flexible alkyl chains. Extending these flexible alkyl chains reduces the crystallinity of the molecules, leading to more uniform dispersion on the electrode surface, which is beneficial for electrochemical performance.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] The first aspect of this invention provides a lithium-ion battery cathode material having a structure as shown in general formula (I):

[0007]

[0008] In formula (I), n is an integer from 3 to 10, and X is one of O, S, C(CH3)2 or NCH3.

[0009] According to an embodiment of the present invention, in formula (I), n is an integer from 5 to 9, and X is S.

[0010] According to embodiments of the present invention, the specific structure of the above-mentioned lithium-ion battery cathode material is any one of the structures shown in formulas (I-1) to (I-32):

[0011]

[0012]

[0013]

[0014]

[0015] A second aspect of the present invention provides a method for preparing a lithium-ion battery cathode material, the method comprising:

[0016] A compound having a structure as shown in general formula (II) and a compound having a structure as shown in general formula (III) are coupled together to obtain a lithium-ion battery cathode material having a structure as shown in general formula (I).

[0017]

[0018] In the formula, n is an integer from 3 to 10, X is one of O, S, C(CH3)2 or NCH3, and Y is one of Cl, Br or I.

[0019] According to an embodiment of the present invention, the above preparation method includes:

[0020] At 0–5 °C, the compound with the structure shown in general formula (II) and the alkali metal hydride were added sequentially to an organic solvent and stirred and dissolved under a protective atmosphere to obtain a mixture;

[0021] A compound with the structure shown in general formula (III) was added to the above mixture to carry out a coupling reaction, thereby obtaining the above lithium-ion battery cathode material.

[0022] According to an embodiment of the present invention, the above-mentioned alkali metal hydride is at least one of sodium hydride or calcium hydride.

[0023] According to an embodiment of the present invention, the organic solvent is at least one of N,N-dimethylformamide or dimethylacetamide.

[0024] According to an embodiment of the present invention, the coupling reaction time is 0.5 to 4.0 h.

[0025] According to an embodiment of the present invention, the molar ratio of the compound having the structure shown in general formula (II) to the compound having the structure shown in general formula (III) is (2.1 to 2.5):1.

[0026] According to an embodiment of the present invention, the molar ratio of the catalyst to the compound having the structure shown in general formula (II) is (1.2 to 1.5):1.

[0027] A third aspect of the present invention provides a lithium-ion battery positive electrode, which includes the lithium-ion battery positive electrode material described above or the lithium-ion battery positive electrode material prepared by the above preparation method.

[0028] According to an embodiment of the present invention, the above-mentioned lithium-ion battery cathode further includes carbon additives and binders.

[0029] According to embodiments of the present invention, the carbon additives include at least one of Super P conductive carbon black, acetylene black, Ketjen black, graphene, graphite, ordered mesoporous carbon, or activated carbon.

[0030] The fourth aspect of the present invention provides a lithium-ion battery, which includes the lithium-ion battery positive electrode material described above or the lithium-ion battery positive electrode material prepared by the above preparation method or the lithium-ion battery positive electrode described above.

[0031] According to embodiments of the present invention, an organic small molecule compound formed by two dibenzo-6-membered rings connected by an alkyl chain is used as the cathode material for lithium-ion batteries. This cathode material uses two dibenzo-6-membered ring structural units as electrochemical redox centers. During charging, the electrons of the nitrogen atoms in the dibenzo-6-membered ring structural units are eliminated from the HOMO orbitals, resulting in a high redox voltage exceeding 3.4V, which is beneficial to improving the energy density of the battery. By adjusting the crystallinity of the molecule through the flexible alkyl chain in the middle, the cathode material is more uniformly dispersed on the electrode surface, which is beneficial to its electrochemical performance. This improves the structural stability, cycle performance, and rate performance of the lithium-ion battery cathode material, and it is expected to be used in next-generation high-voltage, long-cycle-life, high-rate-performance, green and sustainable energy storage batteries.

[0032] According to embodiments of the present invention, the intermediate flexible alkyl chain can alter the density of molecular packing and intermolecular forces in the lithium-ion battery cathode material. Through intermolecular π-π interactions, the intermediate state of the redox process is stabilized, thereby enabling the lithium-ion battery cathode material to achieve better cycle stability. Experiments have demonstrated that this high-voltage organic cathode material exhibits a long cycle life of 10,000 cycles at 50C.

[0033] According to embodiments of the present invention, during the charging and discharging process of a lithium-ion battery, the nitrogen atoms in the dibenzo-6-membered ring structural unit undergo reversible oxidation, forming positively charged cation radicals by losing electrons. The charge of these cations is compensated by counterion anions in the electrolyte, resulting in a faster rate capability for lithium-ion batteries compared to inorganic rigid materials. Experiments have shown that the positive electrode material of lithium-ion batteries can still operate normally at rates up to 100C.

[0034] According to embodiments of the present invention, the method for preparing lithium-ion battery cathode materials provided by the present invention has the advantages of abundant and readily available raw materials, environmental friendliness, low price, and simple synthesis process. Attached Figure Description

[0035] The above and other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the invention with reference to the accompanying drawings, in which:

[0036] Figure 1 This is a scanning electron microscope image of the positive electrode of a lithium-ion battery provided in Embodiment 1 of the present invention;

[0037] Figure 2 This is a charge-discharge curve diagram of the lithium-ion battery provided in Example 1 of the present invention;

[0038] Figure 3 This is a scanning electron microscope image of the positive electrode of a lithium-ion battery provided in Embodiment 2 of the present invention;

[0039] Figure 4 This is a charge-discharge curve diagram of the lithium-ion battery provided in Example 2 of the present invention;

[0040] Figure 5 This is a schematic diagram of the intermolecular forces of the lithium-ion battery cathode material provided in Embodiment 3 of the present invention;

[0041] Figure 6 This is a scanning electron microscope image of the positive electrode of a lithium-ion battery provided in Embodiment 3 of the present invention;

[0042] Figure 7 This is a charge-discharge curve of the lithium-ion battery provided in Example 3 of this invention;

[0043] Figure 8 This is a charge-discharge curve of the lithium-ion battery provided in Example 4 of this invention;

[0044] Figure 9 This is a rate performance diagram of the lithium-ion battery provided in Example 4 of this invention; and

[0045] Figure 10 This is a cycle performance diagram of the lithium-ion battery provided in Example 4 of this invention. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0047] Research revealed that organic electrode materials in related technologies suffer from low discharge plateau voltages, poor structural stability, and inadequate cycle and rate performance. In developing this invention, it was discovered that by designing the molecular structure and controlling the molecular crystallinity, the state of the organic cathode material during charge and discharge can be effectively stabilized, thereby improving the discharge plateau voltage and enhancing cycle and rate performance.

[0048] To address the above problems, the present invention provides a lithium-ion battery cathode material having a structure as shown in general formula (I):

[0049]

[0050] (I)

[0051] In formula (I), n is an integer from 3 to 10, and X is one of O, S, C(CH3)2 or NCH3.

[0052] According to an embodiment of the present invention, n can be any integer from 3 to 10, for example, it can be 3, 4, 5, 6, 7, 8, 9 or 10.

[0053] According to an embodiment of the present invention, O is an oxygen atom and S is a sulfur atom.

[0054] According to embodiments of the present invention, an organic small molecule compound formed by two dibenzo-6-membered rings connected by an alkyl chain is used as the cathode material for lithium-ion batteries. This cathode material uses two dibenzo-6-membered ring structural units as electrochemical redox centers. During charging, the electrons of the nitrogen atoms in the dibenzo-6-membered ring structural units are eliminated from the HOMO orbitals, resulting in a high redox voltage exceeding 3.4V, which is beneficial to improving the energy density of the battery. By adjusting the crystallinity of the molecule through the flexible alkyl chain in the middle, the cathode material is more uniformly dispersed on the electrode surface, which is beneficial to its electrochemical performance. This improves the structural stability, cycle performance, and rate performance of the lithium-ion battery cathode material, and it is expected to be used in next-generation high-voltage, long-cycle-life, high-rate-performance, green and sustainable energy storage batteries.

[0055] According to embodiments of the present invention, the intermediate flexible alkyl chain can alter the density of molecular packing and intermolecular forces in the lithium-ion battery cathode material. Through intermolecular π-π interactions, the intermediate state of the redox process is stabilized, thereby enabling the lithium-ion battery cathode material to achieve better cycle stability. Experiments have demonstrated that this high-voltage organic cathode material exhibits a long cycle life of 10,000 cycles at 50C.

[0056] According to embodiments of the present invention, during the charging and discharging process of a lithium-ion battery, the nitrogen atoms in the dibenzo-6-membered ring structural unit undergo reversible oxidation, forming positively charged cation radicals by losing electrons. The charge of these cations is compensated by counterion anions in the electrolyte, resulting in a faster rate capability for lithium-ion batteries compared to inorganic rigid materials. Experiments have shown that the positive electrode material of lithium-ion batteries can still operate normally at rates up to 100C.

[0057] According to an embodiment of the present invention, in formula (I), n is an integer from 5 to 9, and X is S.

[0058] According to an embodiment of the present invention, n can be any integer from 5 to 9, for example, it can be 5, 6, 7, 8 or 9.

[0059] According to embodiments of the present invention, the specific structure of the above-mentioned lithium-ion battery cathode material is any one of the structures shown in formulas (I-1) to (I-32):

[0060]

[0061]

[0062]

[0063] According to embodiments of the present invention, the introduction of O, S atoms or C(CH3)2, NCH3 groups can enable lithium-ion battery cathode materials to have a high redox voltage of over 3.4V, while also affecting the compactness of molecular packing and intermolecular interactions of lithium-ion battery cathode materials. Therefore, when X in general formula (I) is O, S, C(CH3)2 or NCH3, lithium-ion battery cathode materials can achieve the technical effects of the present invention.

[0064] A second aspect of this invention provides a method for preparing a lithium-ion battery cathode material, the method comprising:

[0065] A compound having a structure as shown in general formula (II) and a compound having a structure as shown in general formula (III) are coupled together to obtain a lithium-ion battery cathode material having a structure as shown in general formula (I).

[0066]

[0067] In the formula, n is an integer from 3 to 10, X is one of O, S, C(CH3)2 or NCH3, and Y is one of Cl, Br or I.

[0068] According to an embodiment of the present invention, n can be any integer from 3 to 10, for example, it can be 3, 4, 5, 6, 7, 8, 9 or 10.

[0069] According to an embodiment of the present invention, O is an oxygen atom and S is a sulfur atom.

[0070] According to an embodiment of the present invention, Y is preferably Br.

[0071] According to an embodiment of the present invention, the above coupling reaction is a CN coupling reaction.

[0072] According to embodiments of the present invention, the specific structure of the above-mentioned compound having the structure shown in general formula (II) is any one of the structures shown in formulas (II-1) to (II-4):

[0073]

[0074]

[0075] According to embodiments of the present invention, the method for preparing lithium-ion battery cathode materials provided by the present invention has the advantages of abundant and readily available raw materials, environmental friendliness, low price, and simple synthesis process.

[0076] According to an embodiment of the present invention, the preparation method of the above-mentioned lithium-ion battery cathode material includes:

[0077] At 0–5 °C, the compound with the structure shown in general formula (II) and the alkali metal hydride were added sequentially to an organic solvent and stirred and dissolved under a protective atmosphere to obtain a mixture;

[0078] A compound with the structure shown in general formula (III) was added to the above mixture to carry out a coupling reaction, thereby obtaining the above lithium-ion battery cathode material.

[0079] According to an embodiment of the present invention, the preparation of lithium-ion battery cathode material can be carried out in an ice-water bath.

[0080] According to embodiments of the present invention, the protective atmosphere introduced during the preparation of the lithium-ion battery cathode material can be any atmosphere that protects the reaction process. For example, it can be an inert gas, specifically, for example, one of nitrogen, argon, or helium.

[0081] According to an embodiment of the present invention, the alkali metal hydride is at least one of sodium hydride or calcium hydride.

[0082] According to embodiments of the present invention, the alkali metal hydride may be sodium hydride or calcium hydride, or a mixture of sodium hydride and calcium hydride in any proportion, preferably sodium hydride.

[0083] According to embodiments of the present invention, the organic solvent is at least one of N,N-dimethylformamide or dimethylacetamide.

[0084] According to embodiments of the present invention, the organic solvent may be N,N-dimethylformamide or dimethylacetamide, or a mixture of N,N-dimethylformamide and dimethylacetamide in any proportion, preferably N,N-dimethylformamide.

[0085] According to an embodiment of the present invention, the coupling reaction time is 0.5 to 4.0 h.

[0086] According to embodiments of the present invention, the coupling reaction time can be 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h or 4h, preferably 0.5h.

[0087] According to an embodiment of the present invention, the molar ratio of the compound having the structure shown in general formula (II) to the compound having the structure shown in general formula (III) is (2.1 to 2.5): 1.

[0088] According to embodiments of the present invention, the molar ratio of the compound having the structure shown in general formula (II) to the compound having the structure shown in general formula (III) can be 2.1:1, 2.2:1, 2.3:1, 2.4:1 or 2.5:1, preferably 2.1:1.

[0089] According to embodiments of the present invention, an excess of a compound having the structure shown in general formula (II) can make the reaction more complete.

[0090] According to an embodiment of the present invention, the molar ratio of the catalyst to the compound having the structure shown in general formula (II) is (1.2 to 1.5):1.

[0091] According to embodiments of the present invention, the molar ratio of the catalyst to the compound having the structure shown in general formula (II) can be 1.2:1, 1.3:1, 1.4:1 or 1.5:1, preferably 1.2:1.

[0092] According to an embodiment of the present invention, an excess of alkali metal hydride makes the reaction more complete.

[0093] According to an embodiment of the present invention, water can be added to the mixture after the coupling reaction is completed to quench the reaction. The organic layer is then collected with dichloromethane, dried with anhydrous sodium sulfate, and concentrated by rotary evaporation. The crude product is purified by silica gel column chromatography using petroleum ether / dichloromethane as the eluent to obtain the lithium-ion battery cathode material.

[0094] A third aspect of the present invention provides a lithium-ion battery positive electrode, which includes the lithium-ion battery positive electrode material described above or the lithium-ion battery positive electrode material prepared by the above preparation method.

[0095] According to embodiments of the present invention, the positive electrode of a lithium-ion battery further includes carbon additives and binders.

[0096] According to an embodiment of the present invention, the positive electrode of a lithium-ion battery may include 3.5 to 9.0 parts of lithium-ion battery positive electrode material, 0.5 to 4.5 parts of carbon additive and 0.5 to 1 part of binder.

[0097] According to embodiments of the present invention, the binder can be any binder applicable to batteries, such as at least one of polyvinylidene fluoride, polytetrafluoroethylene, or sodium carboxymethyl cellulose.

[0098] According to embodiments of the present invention, the carbon additives include at least one of Super P conductive carbon black, acetylene black, Ketjen black, graphene, graphite, ordered mesoporous carbon, or activated carbon.

[0099] According to an embodiment of the present invention, the ordered mesoporous carbon can be CMK-3, and the activated carbon can be YP-80F.

[0100] According to embodiments of the present invention, the carbon additives described above may include conductive carbon additives and supported carbon additives.

[0101] According to an embodiment of the present invention, a lithium-ion battery positive electrode can be prepared by the following method: uniformly mixing and grinding lithium-ion battery positive electrode material, carbon additive and binder to obtain a mixture; dispersing the above mixture in an organic solution to obtain a mixed slurry; coating the above mixed slurry on a current collector and drying it to obtain a lithium-ion battery positive electrode.

[0102] According to embodiments of the present invention, the current collector can be aluminum foil / mesh, stainless steel foil / mesh, carbon-coated aluminum foil, or nickel foam, etc.

[0103] Specifically, the positive electrode for lithium-ion batteries can be prepared by the following method: 3.5–9.0 parts of organic positive electrode material, 0.5–4.5 parts of carbon additive, and 0.5–1 part of binder are uniformly mixed and ground. Then, they are mixed in an N-methylpyrrolidone solution and stirred at room temperature for 0.5–2 hours to form a well-dispersed slurry. The resulting slurry is coated onto a current collector using a doctor blade and dried in a forced-air drying oven at 60–100°C. The positive electrode material is then punched into discs with a diameter of 10–16 mm. These discs are then dried in a vacuum oven at 80–120°C for 3–5 hours at a vacuum pressure of 100 Pa to -1 MPa.

[0104] The fourth aspect of the present invention provides a lithium-ion battery, which includes the lithium-ion battery positive electrode material described above or the lithium-ion battery positive electrode material prepared by the above preparation method or the lithium-ion battery positive electrode described above.

[0105] According to an embodiment of the present invention, a lithium-ion battery can be prepared by the following method: transferring the prepared lithium-ion battery positive electrode into a glove box filled with a protective atmosphere, using lithium metal foil as the negative electrode, separating the positive and negative electrodes with a separator, injecting an electrolyte of 0.1 to 2.0 mol / L, and assembling it into a lithium-ion battery.

[0106] According to embodiments of the present invention, the above-mentioned separator can be any battery separator, such as polypropylene, polyethylene or glass fiber.

[0107] According to embodiments of the present invention, the electrolyte can be a solution obtained by dissolving a lithium-containing inorganic salt in an organic solvent. The lithium salt can be at least one of lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), or lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The electrolyte solvent can be at least one of propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dioxane (DOL), dimethyl glycol ether (DME), and triethylene glycol dimethyl ether (TEGDME).

[0108] According to embodiments of the present invention, the lithium-ion battery cathode material provided by the present invention produces a battery with a stable structure, excellent cycle performance and rate performance, capable of withstanding high voltage and high current, and exhibiting excellent cycle stability. Experiments have shown that within an electrochemical window of 3.0–4.0 V, the material retains up to 75% of its capacity after 10,000 cycles at a high rate of 50C.

[0109] The following detailed description provides several specific embodiments to illustrate the technical solution of the present invention. It should be noted that the specific embodiments described below are merely examples and are not intended to limit the scope of the invention.

[0110] Example 1

[0111] This embodiment provides a lithium-ion battery cathode material with the specific structure shown in formula (I26), prepared by the following method:

[0112] Under ice-water bath conditions, a compound having the structure shown in general formula (II-2) and sodium hydride were added to a solution of N,N-dimethylformamide (DMF) and stirred for 30 minutes under a nitrogen atmosphere. Then, 1,4-dibromobutane was added dropwise while stirring continued. After 4 hours of reaction, a TLC sample was taken, showing no remaining starting material B, indicating complete reaction. The molar ratio of the compound having the structure shown in general formula (II-2) to 1,4-dibromobutane was 2.1:1, and the molar ratio of sodium hydride to the compound having the structure shown in general formula (II-2) was 1.2:1.

[0113] Water was added to the mixture to quench the reaction. The organic layer was collected with dichloromethane, dried with anhydrous sodium sulfate, and concentrated by rotary evaporation. The crude product was purified by silica gel column chromatography using petroleum ether / dichloromethane as the eluent to obtain a lithium-ion battery cathode material with the structure shown in formula (I26).

[0114] The prepared lithium-ion battery cathode material with the structure shown in formula (I26) was characterized by proton NMR, carbon NMR, and high-resolution mass spectrometry. The characterization data are as follows: 1 H-NMR (400MHz, CDCl3) δ (ppm): 7.15-7.06 (m, 8H), 6.89 (td, J1=7.4Hz, J2=1.1Hz, 4H), 6.79 (d, J=8.0Hz, 4H), 3.90-3.83 (m, 4H), 1.94 (m, 4H). 13 C NMR (100MHz, CDCl3) δ (ppm): 145.24, 127.59, 127.34, 125.3, 122.56, 115.65, 46.69, 24.03. HRMS (ESI), m / z: [M+Na] + calcd.for C 28 H 24 N2NaS2, 475.1273; found, 475.1255.

[0115] This embodiment also provides a lithium-ion battery, which is prepared by the following method:

[0116] 40 mg of lithium-ion battery cathode material with the structure shown in formula (I26), 40 mg of conductive carbon additive SuperP, and 20 mg of binder polyvinylidene fluoride were uniformly mixed and ground to obtain a mixture. The mixture was then mixed in an N-methylpyrrolidone solution and stirred at room temperature for 1.5 hours to form a well-dispersed slurry. The slurry was coated onto a current collector using a doctor blade and dried in a forced-air drying oven at 60°C. The cathode material was punched into discs with a diameter of 10 mm. These discs were then dried in a vacuum oven at 100°C for 4 hours at a vacuum pressure of -1 MPa to obtain the lithium-ion battery cathode.

[0117] The prepared lithium-ion battery cathode was examined using a scanning electron microscope, and the results are as follows: Figure 1 As shown.

[0118] The positive electrode of the lithium-ion battery was transferred to a glove box filled with argon atmosphere. A lithium foil was used as the negative electrode, and a separator was placed between the positive and negative electrodes. A 1.0 mol / L LiPF6 electrolyte was injected to assemble the lithium-ion battery. The electrolyte solvent used was a mixture of propylene carbonate (PC) and ethylene carbonate (EC) in equal volumes.

[0119] The prepared lithium-ion battery was subjected to charge-discharge tests at a charge-discharge rate of 1C. The test results are as follows: Figure 2 As shown.

[0120] Depend on Figure 1 It can be seen that the lithium-ion battery cathode material prepared in this embodiment undergoes crystallization, making it impossible to disperse uniformly with the conductive carbon additive and binder, resulting in a decline in electrochemical performance. This demonstrates the significant influence of the alkyl chain length in the molecule on molecular crystallinity and electrode surface morphology. Figure 2 It can be seen that under the test charge / discharge rate of 1C, the discharge voltage plateau is 3.4V, and the initial discharge capacity is 110mAh g. -1 After 100 cycles, the capacity decreased to 26mAh g. -1 .

[0121] Example 2

[0122] This embodiment provides a lithium-ion battery cathode material with the specific structure shown in formula (I31), prepared by the following method:

[0123] Under ice-water bath conditions, a compound having the structure shown in general formula (II-2) and sodium hydride were added to a solution of N,N-dimethylformamide (DMF) and stirred for 30 minutes under a nitrogen atmosphere. Then, 1,9-dibromononane was added dropwise, and stirring continued. After 4 hours of reaction, a TLC sample was taken, showing no residue of starting material B, indicating that the reaction was complete. The molar ratio of the compound having the structure shown in general formula (II-2) to 1,9-dibromononane was 2.1:1, and the molar ratio of sodium hydride to the compound having the structure shown in general formula (II-2) was 1.2:1.

[0124] Water was added to the mixture to quench the reaction. The organic layer was collected with dichloromethane, dried with anhydrous sodium sulfate, and concentrated by rotary evaporation. The crude product was purified by silica gel column chromatography using petroleum ether / dichloromethane as the eluent to obtain a lithium-ion battery cathode material with the structure shown in formula (I31).

[0125] The prepared lithium-ion battery cathode material with the structure shown in formula (I31) was characterized by proton NMR, carbon NMR, and high-resolution mass spectrometry. The characterization data are as follows: 1 H-NMR (400MHz, CDCl3) δ (ppm): 7.20-7.04 (m, 8H), 6.88 (t, J=7.2Hz, 4H), 6.83 (d, J=8.0Hz, 4H), 3.80 (t, J=7.1Hz, 4H), 1.76 (m, 4H), 1.36 (m, 4H), 1.31-1.21 (m, 6H). 13 C NMR (100MHz, CDCl3) δ (ppm): 145.45, 127.53, 127.25, 124.99, 122.40, 115.48, 47.35, 29.43, 29.11, 26.92, 26.87. HRMS (ESI), m / z: [M] + calcd.for C 33 H 34 N2S2, 522.2158; found, 522.2160.

[0126] This embodiment also provides a lithium-ion battery, which is prepared by the following method:

[0127] 40 mg of lithium-ion battery cathode material with the structure shown in formula (I31), 40 mg of conductive carbon additive SuperP, and 20 mg of binder polyvinylidene fluoride were uniformly mixed and ground to obtain a mixture. The mixture was then mixed in an N-methylpyrrolidone solution and stirred at room temperature for 1.5 hours to form a well-dispersed slurry. The slurry was coated onto a current collector using a doctor blade and dried in a forced-air drying oven at 60°C. The cathode material was punched into discs with a diameter of 10 mm. These discs were then dried in a vacuum oven at 100°C for 4 hours under a vacuum pressure of -1 MPa to obtain the lithium-ion battery cathode.

[0128] The prepared lithium-ion battery cathode was examined using a scanning electron microscope, and the results are as follows: Figure 3 As shown.

[0129] The positive electrode of the lithium-ion battery was transferred to a glove box filled with argon atmosphere. A lithium foil was used as the negative electrode, and a separator was placed between the positive and negative electrodes. A 1.0 mol / L LiPF6 electrolyte was injected to assemble the lithium-ion battery. The electrolyte solvent used was a mixture of propylene carbonate (PC) and ethylene carbonate (EC) in equal volumes. The prepared lithium-ion battery was subjected to charge-discharge tests at a charge-discharge rate of 1C. The test results are as follows: Figure 4 As shown.

[0130] Depend on Figure 3 It can be seen that the lithium-ion battery cathode material prepared in this embodiment exhibits no crystallization and can be uniformly dispersed with conductive carbon additives and binders. From Figure 4 It can be seen that under the test charge / discharge rate of 1C, the discharge voltage plateau is 3.5V, and the initial discharge capacity is 99mAh g. -1 After 100 cycles, the capacity decreased to 65mAh g. -1 This indicates that the material has good cycle stability.

[0131] Example 3

[0132] This embodiment provides a lithium-ion battery cathode material with the specific structure shown in formula (I29), prepared by the following method:

[0133] Under ice-water bath conditions, a compound having the structure shown in general formula (II-2) and sodium hydride were added to a solution of N,N-dimethylformamide (DMF) and stirred for 30 minutes under a nitrogen atmosphere. Then, 1,7-dibromoheptane was added dropwise, and stirring continued. After 4 hours of reaction, a TLC sample was taken, showing no remaining starting material B, indicating complete reaction. The molar ratio of the compound having the structure shown in general formula (II-2) to 1,7-dibromoheptane was 2.1:1, and the molar ratio of sodium hydride to the compound having the structure shown in general formula (II-2) was 1.2:1.

[0134] Water was added to the mixture to quench the reaction. The organic layer was collected with dichloromethane, dried with anhydrous sodium sulfate, and concentrated by rotary evaporation. The crude product was purified by silica gel column chromatography using petroleum ether / dichloromethane as the eluent to obtain a lithium-ion battery cathode material with the structure shown in formula (I29).

[0135] The prepared lithium-ion battery cathode material with the structure shown in formula (I29) was characterized by proton nuclear magnetic resonance (NMR) spectroscopy, carbon NMR spectroscopy, and high-resolution mass spectrometry. The characterization data are as follows: 1 H-NMR (400MHz, CDCl3) δ (ppm): 7.13 (m, 8H), 6.90 (t, J=7.5Hz, 4H), 6.82 (d, J=8.0Hz, 4H), 3.80 (t, J=7.0Hz, 4H), 1.76 (m, 4H), 1.41 (m, 4H), 1.32 (m, 2H). 13 C NMR (100MHz, CDCl3) δ (ppm): 145.39, 127.54, 127.28, 125.04, 122.43, 115.52, 47.30, 28.89, 26.90, 26.80. HRMS (ESI), m / z: [M+Na] + calcd.for C 31 H 30 N2NaS2, 517.1743; found, 517.1730.

[0136] Figure 5 This is a schematic diagram of the intermolecular forces of a lithium-ion battery cathode material with the structure shown in formula (I29). Figure 5 The diagram illustrates the presence of intermolecular CH…N, CH…S, and strong π-π interactions within the molecule, which stabilize the intermediate states of the redox process during charge and discharge, thereby enhancing the material's cycling stability. Compared to Example 1, this demonstrates the crucial role of adjusting the alkyl chain length in improving the cycling stability of this type of material.

[0137] This embodiment also provides a lithium-ion battery, which is prepared by the following method:

[0138] 40 mg of lithium-ion battery cathode material with the structure shown in formula (I29), 40 mg of conductive carbon additive SuperP, and 20 mg of binder polyvinylidene fluoride were uniformly mixed and ground to obtain a mixture. The mixture was then mixed in an N-methylpyrrolidone solution and stirred at room temperature for 1.5 hours to form a well-dispersed slurry. The slurry was coated onto a current collector using a doctor blade and dried in a forced-air drying oven at 60°C. The cathode material was punched into discs with a diameter of 10 mm. These discs were then dried in a vacuum oven at 100°C for 4 hours at a vacuum pressure of -1 MPa to obtain the lithium-ion battery cathode.

[0139] The prepared lithium-ion battery cathode was examined using a scanning electron microscope, and the results are as follows: Figure 6 As shown.

[0140] The positive electrode of the lithium-ion battery was transferred to a glove box filled with argon atmosphere. A lithium foil was used as the negative electrode, and a separator was placed between the positive and negative electrodes. A 1.0 mol / L LiPF6 electrolyte was injected to assemble the lithium-ion battery. The electrolyte solvent used was a mixture of propylene carbonate (PC) and ethylene carbonate (EC) in equal volumes. The prepared lithium-ion battery was subjected to charge-discharge tests at a charge-discharge rate of 1C. The test results are as follows: Figure 7 As shown.

[0141] Depend on Figure 6 It can be seen that the lithium-ion battery cathode material prepared in this embodiment did not undergo crystallization, and it was uniformly dispersed with the conductive carbon additive and binder. Figure 1 , Figure 3 and Figure 6 This demonstrates the significant influence of alkyl chain length in the molecule on molecular crystallinity and electrode surface morphology. Figure 7 It can be seen that under the test charge / discharge rate of 1C, the discharge voltage plateau is 3.5V, and the initial discharge capacity is 98mAh g. -1 After 100 cycles, the capacity decreased to 82mAh g. -1 This indicates that the material has excellent cycle stability.

[0142] Example 4

[0143] This embodiment provides a lithium-ion battery cathode material with the specific structure shown in formula (129). Its preparation method is the same as that in Example 3, and will not be repeated here.

[0144] This embodiment also provides a lithium-ion battery, which is prepared by the following method:

[0145] 35 mg of lithium-ion battery cathode material with the structure shown in formula (I29) was loaded onto 45 mg of YP-80F activated carbon material. 10 mg of conductive carbon additive SuperP and 10 mg of binder polyvinylidene fluoride were added, and the mixture was uniformly mixed and ground to obtain a paste. The paste was then mixed in an N-methylpyrrolidone solution and stirred at room temperature for 1.5 hours to form a well-dispersed slurry. The slurry was coated onto a current collector using a doctor blade and dried in a forced-air drying oven at 60°C. The cathode material was punched into discs with a diameter of 10 mm. These discs were then dried in a vacuum oven at 100°C for 4 hours under a vacuum pressure of -1 MPa to obtain the lithium-ion battery cathode.

[0146] The positive electrode of the lithium-ion battery was transferred to a glove box filled with argon atmosphere. A lithium foil was used as the negative electrode, and a separator was placed between the positive and negative electrodes. A 1.0 mol / L LiPF6 electrolyte was injected to assemble the lithium-ion battery. The electrolyte solvent used was a mixture of propylene carbonate (PC) and ethylene carbonate (EC) in equal volumes.

[0147] The prepared lithium-ion battery was subjected to charge-discharge tests at a charge-discharge rate of 1C. The test results are as follows: Figure 8 As shown. By Figure 8 It can be seen that under the test charge / discharge rate of 1C, the discharge voltage plateau is 3.5V, and the initial discharge capacity is 95mAh g. -1 .

[0148] The rate performance of the prepared lithium-ion battery was tested, and the test results are as follows: Figure 9 As shown. By Figure 9 It can be seen that the material can still operate normally at high rates of 50°C or even 100°C, indicating that the material has excellent rate performance.

[0149] The prepared lithium-ion battery was subjected to cycle stability testing, and the test results are as follows: Figure 10 As shown. By Figure 10 It can be seen that after 10,000 cycles at a high rate of 50C, the capacity retention of this material is still as high as 75%, indicating the excellent cycling performance of this high-voltage organic cathode material. When combined / mixed with two carbon materials, the electrochemical performance of this material is maximized.

[0150] Comparative Example 1

[0151] This comparative example provides a lithium-ion battery cathode material, which is a bis[4-(10H-phenthiazin-10-yl)phenyl]methyl ketone cathode material having the structure shown in formula (V-1).

[0152]

[0153] This comparative example also provides a lithium-ion battery, the preparation method of which is the same as in Example 3, except that the lithium-ion battery cathode material having the structure shown in formula (I29) is replaced with an equal weight of bis[4-(10H-phenthiazin-10-yl)phenyl]methyl ketone cathode material.

[0154] The prepared lithium-ion battery was subjected to charge-discharge tests at a rate of 1C. The test results showed a discharge voltage plateau of 3.64V and an initial capacity of 89.6 mAh g. -1 After 100 laps, the capacity decays to 17.2% of the initial capacity.

[0155] Comparative Example 2

[0156] This comparative example provides a lithium-ion battery cathode material, which is a bis[4-(10H-phenoxazine-10-yl)phenyl]methyl ketone cathode material having the structure shown in formula (V-2).

[0157]

[0158] This comparative example also provides a lithium-ion battery, the preparation method of which is the same as in Example 3, except that the lithium-ion battery cathode material having the structure shown in formula (129) is replaced with an equal weight of bis[4-(10H-phenoxazine-10-yl)phenyl]methyl ketone cathode material, and the electrolyte is 1M LiTFSI in EC∶DEC=1∶1Vol.

[0159] The prepared lithium-ion battery was subjected to charge-discharge tests at a rate of 1C. The test results showed a discharge voltage plateau of 3.60V and an initial capacity of 92.9 mAh g⁻¹. -1 After 100 laps, the capacity decays to 19.2% of the initial capacity.

[0160] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A lithium-ion battery positive electrode, characterized in that, The lithium-ion battery positive electrode includes a lithium-ion battery positive electrode material, which has a structure as shown in general formula (I): （Ⅰ） In equation (Ⅰ), n is an integer from 3 to 10, and X is either O or S.

2. The lithium-ion battery positive electrode according to claim 1, characterized in that, In equation (Ⅰ), n is an integer from 5 to 9, and X is S.

3. The lithium-ion battery positive electrode according to claim 1, characterized in that, The specific structure of the lithium-ion battery cathode material is any one of the structures shown in formulas (I-17) to (I-32):

4. The lithium-ion battery positive electrode according to claim 1, characterized in that, The method for preparing the lithium-ion battery cathode material includes: A compound having the structure shown in general formula (II) and a compound having the structure shown in general formula (III) are coupled together to obtain a lithium-ion battery cathode material having the structure shown in general formula (I). In the formula, n is an integer from 3 to 10, X is one of O and S, and Y is one of Cl, Br or I.

5. The lithium-ion battery positive electrode according to claim 4, characterized in that, The preparation method includes: At 0~5℃, the compound with the structure shown in general formula (II) and the alkali metal hydride are added sequentially to an organic solvent and stirred and dissolved under a protective atmosphere to obtain a mixture; A compound with the structure shown in general formula (III) is added to the mixture to carry out a coupling reaction to obtain the lithium-ion battery cathode material.

6. The lithium-ion battery positive electrode according to claim 5, characterized in that, The alkali metal hydride is at least one of sodium hydride or calcium hydride; The organic solvent is at least one of N,N-dimethylformamide or dimethylacetamide; The coupling reaction takes 0.5 to 4.0 hours. The molar ratio of the compound having the structure shown in general formula (II) to the compound having the structure shown in general formula (III) is (2.1~2.5):1; The molar ratio of the alkali metal hydride to the compound having the structure shown in general formula (II) is (1.2~1.5):

1.

7. The lithium-ion battery positive electrode according to claim 1, characterized in that, The positive electrode of the lithium-ion battery also includes carbon additives and binders.

8. The lithium-ion battery positive electrode according to claim 7, characterized in that, The carbon additive is selected from at least one of Super P conductive carbon black, acetylene black, Ketchen black, graphene, graphite, ordered mesoporous carbon, or activated carbon.

9. A lithium-ion battery, characterized in that, The lithium-ion battery includes the positive electrode of the lithium-ion battery as described in any one of claims 1 to 8.

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