Modified lithium-rich manganese-based positive electrode material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of lithium batteries, and particularly relates to a modified lithium-rich manganese-based positive electrode material and a preparation method and application thereof. The modified lithium-rich manganese-based positive electrode material comprises the following raw materials in parts by mass: 100 parts of a lithium-rich manganese-based positive electrode material and 0.5-5 parts of a thiophene derivative, the thiophene derivative comprises 3-methylthiophene, 3-hexylthiophene, 3, 4-dimethoxythiophene, 3, 4-ethylenedioxythiophene, and thienopyrrole. The invention also discloses a preparation method of the thiophene derivative. The modified lithium-rich manganese-based positive electrode material has the beneficial effects that the modified lithium-rich manganese-based positive electrode material has relatively high specific capacity and relatively good rate capability and cycling stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium batteries, and particularly relates to a modified lithium-rich manganese-based cathode material, a preparation method thereof, and an application thereof. Background Art

[0002] With the development of portable electronic devices, electric vehicles, and energy storage systems, the demand for high-performance lithium-ion batteries is increasing day by day. Lithium-ion batteries have become the mainstream battery technology due to their high energy density, high working voltage, long cycle life, and environmental protection characteristics. The cathode material is the core of a lithium-ion battery, and its performance determines the overall performance of the battery. Lithium-rich manganese-based cathode materials (xLi2MnO3·(1-x)LiTMO2, TM = Ni, Mn, Co, etc.) have become a research hotspot for the next generation of high-energy-density lithium-ion batteries due to their high capacity (>250 mAh / g), low cost, and environmental protection advantages. This material provides high energy density through the insertion / extraction of lithium ions and the redox reaction of transition metal ions.

[0003] Although lithium-rich manganese-based materials have many advantages, they still face challenges in practical applications. For example, lithium-rich manganese-based cathode materials have poor cycle stability, are prone to phase transformation and structural collapse, resulting in capacity decay; their first Coulombic efficiency is low, there are many side reactions on the surface, and the first charge-discharge efficiency is low; there is also a problem of insufficient rate performance and poor electrochemical performance at high rates. Summary of the Invention

[0004] The present application provides a modified lithium-rich manganese-based cathode material, a preparation method thereof, and an application thereof, aiming to solve the problems of low first charge-discharge efficiency, insufficient rate performance, and poor cycle stability of existing lithium-rich manganese-based cathode materials.

[0005] The first aspect of the present application provides a modified lithium-rich manganese-based cathode material, which includes the following raw materials in parts by mass: 100 parts of lithium-rich manganese-based cathode material and 0.5 - 5 parts of thiophene derivative;

[0006] The thiophene derivative includes 3-methylthiophene, 3-hexylthiophene, 3,4-dimethoxythiophene, 3,4-ethylenedioxythiophene, and thiophene并pyrrole.

[0007] The modified lithium-rich manganese-based cathode material of the present application has a high specific capacity, good rate performance, and cycle stability.

[0008] According to some embodiments of the modified lithium-rich manganese-based cathode material of the present application, the chemical formula of the lithium-rich manganese-based cathode material is: xLi2MnO3·(1-x)LiTMO2, where 0 < x < 1, and TM includes one or more of Ni, Mn, and Co.

[0009] According to some embodiments of the modified lithium-rich manganese-based positive electrode material described in the present application, the modified lithium-rich manganese-based positive electrode material includes the following raw materials in parts by mass: 100 parts of lithium-rich manganese-based positive electrode material and 1-3 parts of thiophene derivative.

[0010] According to some embodiments of the modified lithium-rich manganese-based positive electrode material described in the present application, the thiophene derivatives include 3,4-ethylenedioxythiophene and thienopyrrole.

[0011] The second aspect of the present application provides a method for preparing the modified lithium-rich manganese-based positive electrode material described in the first aspect of the present application, comprising the following steps: mixing a lithium-rich manganese-based positive electrode material, a thiophene derivative, an oxidant and a solvent to obtain the modified lithium-rich manganese-based positive electrode material.

[0012] The present application disperses the positive electrode material in a monomer solution by an in-situ oxidative polymerization method, and adds an oxidant for polymerization reaction, which can achieve uniform coating of the conductive polymer and avoid complicated post-processing processes. Compared with other surface modification techniques (such as chemical vapor deposition, sol-gel method, etc.), this method has a simple process and is suitable for large-scale production. The conductive polymer coating layer formed by in-situ polymerization can improve the dispersibility of the positive electrode material particles and reduce the agglomeration of particles. The in-situ polymerization method can accurately control the thickness and structure of the coating layer by adjusting conditions such as monomer concentration, oxidant dosage, reaction time, etc.

[0013] According to some embodiments of the method for preparing the modified lithium-rich manganese-based positive electrode material described in the present application, the oxidant includes one or more of ferric chloride, ammonium persulfate, silver nitrate and hydrogen peroxide.

[0014] According to some embodiments of the method for preparing the modified lithium-rich manganese-based positive electrode material described in the present application, the solvent includes one or more of dichloromethane, chloroform, acetonitrile and methanol.

[0015] According to some embodiments of the method for preparing the modified lithium-rich manganese-based positive electrode material described in the present application, the molar ratio of the amount of the oxidant to the thiophene derivative is (2-3):1.

[0016] According to some embodiments of the method for preparing the modified lithium-rich manganese-based positive electrode material described in the present application, the temperature of the mixing reaction is 0-5° C., and the time of the mixing reaction is 6-24 hours.

[0017] According to some embodiments of the method for preparing the modified lithium-rich manganese-based positive electrode material described in the present application, the mixing reaction is carried out in an inert atmosphere.

[0018] According to some embodiments of the method for preparing the modified lithium-rich manganese-based positive electrode material described in the present application, the inert atmosphere includes a nitrogen atmosphere and / or an argon atmosphere.

[0019] According to some embodiments of the method for preparing the modified lithium-rich manganese-based positive electrode material described in the present application, the preparation method also includes purifying the mixed reaction product.

[0020] According to some embodiments of the method for preparing the modified lithium-rich manganese-based positive electrode material described in the present application, the purification process includes filtering, washing and drying the mixed product in sequence.

[0021] According to some embodiments of the method for preparing the modified lithium-rich manganese-based positive electrode material described in the present application, the detergent used for washing includes one or more of anhydrous ethanol, methanol and water.

[0022] According to some embodiments of the method for preparing the modified lithium-rich manganese-based positive electrode material described in the present application, the drying temperature is 80-100° C., and the drying time is 20-30 hours. DETAILED DESCRIPTION

[0023] Embodiments of the present invention are described in detail below. The examples of the embodiments are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0024] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0025] The embodiment of the present application provides a modified lithium-rich manganese-based positive electrode material, comprising the following raw materials in parts by mass: 100 parts of lithium-rich manganese-based positive electrode material and 0.5-5 parts of thiophene derivative;

[0026] The thiophene derivatives include 3-methylthiophene, 3-hexylthiophene, 3,4-dimethoxythiophene, 3,4-ethylenedioxythiophene, and thienopyrrole.

[0027] The thiophene derivative contained in the modified lithium-rich manganese-based cathode material of the present application has good electrical conductivity. Coating it on the surface of the lithium-rich manganese-based cathode material can bond the cathode material together to form a conductive network, effectively reducing the resistance between particles, accelerating the electron transfer speed between particles, and increasing the electron exchange rate. In addition, the coating layer formed by the thiophene derivative on the surface of the lithium-rich manganese-based cathode material helps to optimize the interfacial properties between the cathode material and the electrolyte. The side chain of the polythiophene derivative with polar groups can improve the compatibility between the components of the cathode material, reduce the interfacial impedance, and promote the transfer of lithium ions.

[0028] Due to the flexibility of the thiophene derivative, it can improve the mechanical strength of the cathode material and enhance its adaptability in high-energy density batteries. Moreover, the coating layer formed by the thiophene derivative can effectively inhibit the structural changes that occur during the charge and discharge process of the lithium-rich manganese-based material, reduce capacity attenuation, and extend the cycle life. The coating of the polythiophene derivative can also prevent the dissolution of manganese to a certain extent during the battery cycle, thereby improving the stability and durability of the material.

[0029] In some embodiments of the present application, the chemical formula of the lithium-rich manganese-based cathode material is: xLi2MnO3·(1 - x)LiTMO2, where 0 < x < 1, and TM includes one or more of Ni, Mn, and Co. The lithium-rich manganese-based cathode material is mainly composed of two components, LiTMO2 with a hexagonal crystal system structure and Li2MnO3 with a monoclinic crystal system structure.

[0030] In some embodiments of the present application, the modified lithium-rich manganese-based cathode material includes the following raw materials in parts by mass: 100 parts of the lithium-rich manganese-based cathode material and 1 - 3 parts of the thiophene derivative. The selection of the ratio or coating amount of the thiophene monomer to the cathode material is a key factor affecting the performance of the cathode material. A reasonable ratio and coating amount can ensure the uniformity and functionality of the coating layer, while avoiding side effects caused by overcoating (such as blocked ion transport and reduced conductivity). A lower coating amount (such as < 1wt%) may not be able to completely cover the surface of the cathode material, resulting in insufficient protection effect. A higher coating amount (such as > 3wt%) may cause the coating layer itself to expand, peel off, or degrade during cycling, affecting long-term stability.

[0031] In some embodiments of the present application, the thiophene derivative includes 3,4-ethylenedioxythiophene and thiophene并pyrrole. 3,4-Ethylenedioxythiophene introduces a methoxy substituent at the 3,4 positions of thiophene, enhancing the electron-donating ability of the monomer. A polymer with relatively high conductivity can be prepared by in-situ oxidative polymerization, which is suitable for application in electrochemical devices. Thiophene并pyrrole is a conjugated heterocyclic monomer of thiophene and pyrrole, and forms a low-bandgap conductive conjugated polymer after polymerization, which is suitable for energy storage devices.

[0032] The embodiment of the present application also provides a method for preparing the modified lithium-rich manganese-based positive electrode material described in the first aspect of the present application, comprising the following steps: mixing and reacting the lithium-rich manganese-based positive electrode material, a thiophene derivative, an oxidant and a solvent to obtain the modified lithium-rich manganese-based positive electrode material. The present application disperses the positive electrode material in a monomer solution by an in-situ oxidative polymerization method, and adds an oxidant for polymerization reaction, which can achieve uniform coating of the conductive polymer and avoid complex post-processing processes. Compared with other surface modification techniques (such as chemical vapor deposition, sol-gel method, etc.), this method has a simple process and is suitable for large-scale production. The conductive polymer coating layer formed by in-situ polymerization can improve the dispersibility of the positive electrode material particles and reduce the agglomeration of particles. The in-situ polymerization method can accurately control the thickness and structure of the coating layer by adjusting conditions such as monomer concentration, oxidant dosage, reaction time, etc.

[0033] In some embodiments of the present application, the oxidant includes one or more of ferric chloride, ammonium persulfate, silver nitrate and hydrogen peroxide.

[0034] Ferric chloride is a commonly used oxidant with strong oxidizing ability. It can easily oxidize thiophene monomers into free radical cations and promote polymerization. Its by-product is FeCl2, which can be easily removed by washing.

[0035] Ammonium persulfate is a strong oxidant, and the byproduct of its oxidation is ammonium sulfate, which can be easily removed by washing.

[0036] In some embodiments of the present application, the solvent includes one or more of dichloromethane, chloroform, acetonitrile and methanol. The solvent selected in the present application has good solubility and has no adverse effect on the by-products of the reaction system.

[0037] In some embodiments of the present application, the molar ratio of the oxidant to the thiophene derivative is (2-3):1, such as 2:1, 2.2:1, 2.5:1, 3:1, etc., to ensure efficient and thorough reaction.

[0038] In some embodiments of the present application, the temperature of the mixed reaction is 0-5°C, for example, 0°C, 2°C, 3°C, 5°C, etc. Controlling at a lower temperature helps to inhibit side reactions (such as over-oxidation). The time of the mixed reaction is 6-24h, for example, 6h, 10h, 12h, 15h, 18h, 20h, 24h, etc. Long reaction time may cause excessive oxidation or degradation of the polymer, and is generally controlled within 6-24 hours.

[0039] In some embodiments of the present application, the mixing reaction is carried out in an inert atmosphere.

[0040] In some embodiments of the present application, the inert atmosphere includes a nitrogen atmosphere and / or an argon atmosphere.

[0041] In some embodiments of the present application, the preparation method further includes purifying the mixed reaction product.

[0042] In some embodiments of the present application, the purification process includes filtering, washing and drying the mixed product in sequence.

[0043] In some embodiments of the present application, the washing agent used in the washing includes one or more of anhydrous ethanol, methanol and water. The washing is performed to remove unreacted monomers and by-products.

[0044] In some embodiments of the present application, the drying temperature is 80-100°C, for example, 80°C, 85°C, 90°C, 95°C, 100°C, etc., and the drying time is 20-30h, for example, 20h, 22h, 26h, 28h, 30h, etc.

[0045] The technical solution of the present application is further described below in conjunction with specific embodiments.

[0046] Example 1

[0047] A method for preparing a modified lithium-rich manganese-based positive electrode material comprises the following steps:

[0048] Thiophene derivative monomer thienopyrrole (1 mmol, 0.1238 g) was mixed with 12.38 g lithium-rich manganese-based positive electrode material Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2 was added to 30 mL of chloroform solvent to obtain mixture A, anhydrous FeCl3 (2.5 mmol, 0.4055 g) was dispersed in 10 mL of chloroform to obtain mixture B, mixture A and mixture B were both subjected to ultrasonic treatment, and then mixture B was slowly added to mixture A for oxidative polymerization reaction. The reaction was carried out under N2 atmosphere. After reacting at 0°C for 24 hours, the crude product was filtered to obtain the crude product, which was washed with anhydrous ethanol, and the washed product was dried in a vacuum drying oven at 80°C for 24 hours to obtain a polythiophene derivative-coated modified lithium-rich manganese-based positive electrode material.

[0049] Example 2

[0050] The preparation method of the modified lithium-rich manganese-based positive electrode material described in Example 2 is different from that in Example 1 only in that, during the preparation process of the modified lithium-rich manganese-based positive electrode material described in Example 2, the amounts of thiophene derivative monomer thiophene pyrrole and lithium-rich manganese-based positive electrode material added are different from those in Example 1.

[0051] The specific steps include:

[0052] Thiophene derivative monomer thienopyrrole (1 mmol, 0.1238 g) was mixed with 24.76 g lithium-rich manganese-based positive electrode material Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2 was added to 40 mL of chloroform solvent to obtain mixture A, anhydrous FeCl3 (2.5 mmol, 0.4055 g) was dispersed in 10 mL of chloroform to obtain mixture B, mixture A and mixture B were both subjected to ultrasonic treatment, and then mixture B was slowly added to mixture A for oxidative polymerization reaction. The reaction was carried out under N2 atmosphere. After reacting at 0°C for 24 hours, the crude product was filtered to obtain the crude product, which was washed with anhydrous ethanol, and the washed product was dried in a vacuum drying oven at 80°C for 24 hours to obtain a polythiophene derivative-coated modified lithium-rich manganese-based positive electrode material.

[0053] Example 3

[0054] The only difference between the preparation method of the modified lithium-rich manganese-based positive electrode material described in Example 3 and that in Example 1 is that during the preparation process of the modified lithium-rich manganese-based positive electrode material described in Example 3, the amounts of thiophene derivative monomer thiophene pyrrole and lithium-rich manganese-based positive electrode material added are different from those in Example 1.

[0055] The specific steps include:

[0056] Thiophene derivative monomer thiophene pyrrole (1 mmol, 0.1238 g) was mixed with 6.19 g lithium-rich manganese-based positive electrode material Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2 was added to 20 mL of chloroform solvent to obtain mixture A, anhydrous FeCl3 (2.5 mmol, 0.4055 g) was dispersed in 10 mL of chloroform to obtain mixture B, mixture A and mixture B were both subjected to ultrasonic treatment, and then mixture B was slowly added to mixture A for oxidative polymerization reaction. The reaction was carried out under N2 atmosphere. After reacting at 0°C for 24 hours, the crude product was filtered to obtain the crude product, which was washed with anhydrous ethanol, and the washed product was dried in a vacuum drying oven at 80°C for 24 hours to obtain a polythiophene derivative-coated modified lithium-rich manganese-based positive electrode material.

[0057] Example 4

[0058] The preparation method of the modified lithium-rich manganese-based positive electrode material described in Example 4 is different from that in Example 1 only in that, during the preparation process of the modified lithium-rich manganese-based positive electrode material described in Example 4, the amounts of thiophene derivative monomer thiophene pyrrole and lithium-rich manganese-based positive electrode material added are different from those in Example 1.

[0059] The specific steps include:

[0060] Thiophene derivative monomer thiophene pyrrole (1 mmol, 0.1238 g) was mixed with 4.126 g lithium-rich manganese-based positive electrode material Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2 was added to 15 mL of chloroform solvent to obtain mixture A, anhydrous FeCl3 (2.5 mmol, 0.4055 g) was dispersed in 10 mL of chloroform to obtain mixture B, mixture A and mixture B were both subjected to ultrasonic treatment, and then mixture B was slowly added to mixture A for oxidative polymerization reaction. The reaction was carried out under N2 atmosphere. After reacting at 0°C for 24 hours, the crude product was filtered to obtain the crude product, which was washed with anhydrous ethanol, and the washed product was dried in a vacuum drying oven at 80°C for 24 hours to obtain a polythiophene derivative-coated modified lithium-rich manganese-based positive electrode material.

[0061] Example 5

[0062] The only difference between the preparation method of the modified lithium-rich manganese-based positive electrode material described in Example 5 and that in Example 1 is that during the preparation process of the modified lithium-rich manganese-based positive electrode material described in Example 5, the amounts of thiophene derivative monomer thiophene pyrrole and lithium-rich manganese-based positive electrode material added are different from those in Example 1.

[0063] The specific steps include:

[0064] Thiophene derivative monomer thiophene pyrrole (1 mmol, 0.1238 g) was mixed with 2.476 g lithium-rich manganese-based positive electrode material Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2 was added to 10 mL of chloroform solvent to obtain mixture A, anhydrous FeCl3 (2.5 mmol, 0.4055 g) was dispersed in 10 mL of chloroform to obtain mixture B, mixture A and mixture B were both subjected to ultrasonic treatment, and then mixture B was slowly added to mixture A for oxidative polymerization reaction, the reaction was carried out under N2 atmosphere, and after reacting at 0°C for 24 hours, the crude product was filtered to obtain the crude product, which was washed with anhydrous ethanol, and the washed product was dried in a vacuum drying oven at 80°C for 24 hours to obtain a polythiophene derivative-coated modified lithium-rich manganese-based positive electrode material.

[0065] Example 6

[0066] The preparation method of the modified lithium-rich manganese-based positive electrode material described in Example 6 is different from that of Example 1 only in that, in the preparation process of the modified lithium-rich manganese-based positive electrode material described in Example 6, 3-methylthiophene is used instead of the thiophene derivative monomer thienopyrrole

[0067] The specific steps include:

[0068] Thiophene derivative monomer 3-methylthiophene (1 mmol, 0.0982 g) was mixed with 9.82 g lithium-rich manganese-based cathode material Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2 was added to 20 mL of chloroform solvent to obtain mixture A, anhydrous FeCl3 (2.5 mmol, 0.4055 g) was dispersed in 10 mL of chloroform to obtain mixture B, mixture A and mixture B were both subjected to ultrasonic treatment, and then mixture B was slowly added to mixture A for oxidative polymerization reaction. The reaction was carried out under N2 atmosphere. After reacting at 0°C for 24 hours, the crude product was filtered to obtain the crude product, which was washed with anhydrous ethanol, and the washed product was dried in a vacuum drying oven at 80°C for 24 hours to obtain a polythiophene derivative-coated modified lithium-rich manganese-based positive electrode material.

[0069] Example 7

[0070] The preparation method of the modified lithium-rich manganese-based positive electrode material described in Example 7 is different from that of Example 1 only in that, in the preparation process of the modified lithium-rich manganese-based positive electrode material described in Example 7, 3-hexylthiophene is used instead of the thiophene derivative monomer thienopyrrole

[0071] The specific steps include:

[0072] Thiophene derivative monomer 3-hexylthiophene (1 mmol, 0.1683 g) was mixed with 16.83 g lithium-rich manganese-based positive electrode material Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2 was added to 20 mL of chloroform solvent to obtain mixture A, anhydrous FeCl3 (2.5 mmol, 0.4055 g) was dispersed in 10 mL of chloroform to obtain mixture B, mixture A and mixture B were both subjected to ultrasonic treatment, and then mixture B was slowly added to mixture A for oxidative polymerization reaction. The reaction was carried out under N2 atmosphere. After reacting at 0°C for 24 hours, the crude product was filtered to obtain the crude product, which was washed with anhydrous ethanol, and the washed product was dried in a vacuum drying oven at 80°C for 24 hours to obtain a polythiophene derivative-coated modified lithium-rich manganese-based positive electrode material.

[0073] Example 8

[0074] The preparation method of the modified lithium-rich manganese-based positive electrode material described in Example 8 is different from that of Example 1 only in that, in the preparation process of the modified lithium-rich manganese-based positive electrode material described in Example 8, 3,4-dimethoxythiophene is used instead of the thiophene derivative monomer thienopyrrole

[0075] The specific steps include:

[0076] Thiophene derivative monomer 3,4-dimethoxythiophene (1 mmol, 0.1122 g) was mixed with 11.22 g lithium-rich manganese-based cathode material Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2 was added to 30 mL of chloroform solvent to obtain mixture A, anhydrous FeCl3 (2.5 mmol, 0.4055 g) was dispersed in 10 mL of chloroform to obtain mixture B, mixture A and mixture B were both subjected to ultrasonic treatment, and then mixture B was slowly added to mixture A for oxidative polymerization reaction. The reaction was carried out under N2 atmosphere. After reacting at 0°C for 24 hours, the crude product was filtered to obtain the crude product, which was washed with anhydrous ethanol, and the washed product was dried in a vacuum drying oven at 80°C for 24 hours to obtain a polythiophene derivative-coated modified lithium-rich manganese-based positive electrode material.

[0077] Example 9

[0078] The preparation method of the modified lithium-rich manganese-based positive electrode material described in Example 9 is different from that of Example 1 only in that, in the preparation process of the modified lithium-rich manganese-based positive electrode material described in Example 9, 3,4-ethylenedioxythiophene is used instead of thiophene derivative monomer thienopyrrole

[0079] The specific steps include:

[0080] Thiophene derivative monomer 3,4-ethylenedioxythiophene (1 mmol, 0.1422 g) was mixed with 14.22 g lithium-rich manganese-based positive electrode material Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2 was added to 30 mL of chloroform solvent to obtain mixture A, anhydrous FeCl3 (2.5 mmol, 0.4055 g) was dispersed in 10 mL of chloroform to obtain mixture B, mixture A and mixture B were both subjected to ultrasonic treatment, and then mixture B was slowly added to mixture A for oxidative polymerization reaction. The reaction was carried out under N2 atmosphere. After reacting at 0°C for 24 hours, the crude product was filtered to obtain the crude product, which was washed with anhydrous ethanol, and the washed product was dried in a vacuum drying oven at 80°C for 24 hours to obtain a polythiophene derivative-coated modified lithium-rich manganese-based positive electrode material.

[0081] Comparative Example 1

[0082] The only difference between the preparation method of the modified lithium-rich manganese-based positive electrode material described in Comparative Example 1 and that of Example 1 is that, in the preparation process of the modified lithium-rich manganese-based positive electrode material described in Comparative Example 1, thiophene is used instead of the thiophene derivative monomer thienopyrrole.

[0083] The specific steps include:

[0084] Thiophene monomer (1 mmol, 0.0841 g) was mixed with 8.41 g of lithium-rich manganese-based cathode material Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2 was added to 30 mL of chloroform solvent to obtain mixture A, anhydrous FeCl3 (2.5 mmol, 0.4055 g) was dispersed in 10 mL of chloroform to obtain mixture B, mixture A and mixture B were both subjected to ultrasonic treatment, and then mixture B was slowly added to mixture A for oxidative polymerization reaction. The reaction was carried out under N2 atmosphere. After reacting at 0°C for 24 hours, the crude product was filtered to obtain the crude product, which was washed with anhydrous ethanol, and the washed product was dried in a vacuum drying oven at 80°C for 24 hours to obtain a polythiophene derivative-coated modified lithium-rich manganese-based positive electrode material.

[0085] Study on the electrical properties of the modified lithium-rich manganese-based positive electrode materials described in Examples 1-9 and Comparative Example 1 of the present application

[0086] The modified lithium-rich manganese-based positive electrode materials described in Examples 1-9 and Comparative Example 1 are slurry-coated to prepare positive electrode sheets and assembled with buckles:

[0087] The modified lithium-rich manganese-based positive electrode materials described in Examples 1-9 and Comparative Example 1 were mixed with acetylene black conductive agent and polyvinylidene fluoride (PVDF) binder (the mass fraction of polyvinylidene fluoride is 8%, and the solvent is N-methylpyrrolidone) in a mass ratio of 8:1:1, and fully stirred to form a uniform viscous slurry. The slurry was evenly coated on aluminum foil, and then dried at 80°C under vacuum conditions for 12 hours. The dried pole pieces were cut into 12 mm discs as positive pole pieces.

[0088] The assembly of CR2032 button cells was carried out in an argon-filled glove box with oxygen and water contents below 0.1 ppm.

[0089] 1M LiPF6 is used as the electrolyte, dissolved in a mixed solvent of EC (ethylene carbonate) and DMC (dimethyl carbonate) in a volume ratio of 1:1 to prepare the electrolyte. The battery assembly sequence is: first place the positive electrode shell, then place the positive electrode sheet, diaphragm, lithium sheet, nickel foam and negative electrode shell in turn. After completing this series of assemblies, the battery is packaged on the packaging machine. After the assembled and packaged battery is placed under constant temperature conditions for 24 hours, the charge and discharge test is carried out.

[0090] Electrochemical performance test: Xinwei equipment was used to conduct electrochemical performance related tests, using 1C = 250mAg -1 The voltage range of the battery during charge and discharge is 2.0-4.8V (vs. Li / Li +), all electrochemical performance tests were carried out at room temperature 25°C, and the corresponding electrochemical performance test results are shown in Table 1.

[0091] Table 1

[0092]

[0093]

[0094] It can be seen from Table 1 that the lithium-rich manganese-based positive electrode material modified by coating polythiophene pyrrole and poly 3,4-ethylenedioxythiophene has a higher specific capacity, better rate performance and cycle stability, and it is more appropriate to control the coating amount of the polythiophene derivative at 1-3w%. Too low or too high will have a negative impact on the coating modification effect.

[0095] Although the above embodiments have been shown and described, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. Changes, modifications, substitutions and variations of the above embodiments by those of ordinary skill in the art are all within the scope of protection of the present invention.

Claims

1. A modified lithium-rich manganese-based positive electrode material, characterized in that: Comprising the following parts by mass of raw materials: 100 parts of lithium-rich manganese-based cathode material and 0.5 - 5 parts of thiophene derivative; The thiophene derivative includes 3-methylthiophene, 3-hexylthiophene, 3,4-dimethoxythiophene, 3,4-ethylenedioxythiophene, thiophene并pyrrole. (It seems there is a typo here, it might be "thiophene并pyrrole" which is not a common name. Maybe it should be "thiophenopyrrole"?) 2. The modified lithium-rich manganese-based positive electrode material according to claim 1, characterized in that: The chemical formula of the lithium-rich manganese-based cathode material is: xLi2MnO3·(1 - x)LiTMO2, where 0 < x < 1, and TM includes one or more of Ni, Mn, and Co.

3. The modified lithium-rich manganese-based positive electrode material according to claim 1, characterized in that: Comprising the following parts by mass of raw materials: 100 parts of lithium-rich manganese-based cathode material and 1 - 3 parts of thiophene derivative; And / or, the thiophene derivative includes 3,4-ethylenedioxythiophene, thiophene并pyrrole. (Same as above, might be a typo. Assuming it should be "thiophenopyrrole") 4. The method for preparing the modified lithium-rich manganese-based positive electrode material according to any one of claims 1 to 3, characterized in that: Including the following steps: Mixing and reacting the lithium-rich manganese-based cathode material, thiophene derivative, oxidant, and solvent to obtain the modified lithium-rich manganese-based cathode material.

5. The method for preparing the modified lithium-rich manganese-based positive electrode material according to claim 4, characterized in that: The oxidant includes one or more of ferric chloride, ammonium persulfate, silver nitrate, and hydrogen peroxide; And / or, the solvent includes one or more of dichloromethane, chloroform, acetonitrile, and methanol.

6. The method for preparing the modified lithium-rich manganese-based positive electrode material according to claim 4, characterized in that: The molar ratio of the amount of the oxidant to the thiophene derivative is (2 - 3):

1.

7. The method for preparing the modified lithium-rich manganese-based positive electrode material according to claim 4, characterized in that: The temperature of the mixing reaction is 0 - 5°C, and the time of the mixing reaction is 6 - 24 h.

8. The method for preparing the modified lithium-rich manganese-based positive electrode material according to claim 4, characterized in that: The mixing reaction is carried out in an inert atmosphere; Preferably, the inert atmosphere includes a nitrogen atmosphere and / or an argon atmosphere.

9. The method for preparing the modified lithium-rich manganese-based positive electrode material according to claim 4, characterized in that: The preparation method further includes purifying the mixing reaction product; Preferably, the purification treatment includes sequentially filtering, washing, and drying the mixed product.

10. The method for preparing the modified lithium-rich manganese-based positive electrode material according to claim 9, characterized in that: The detergent used for washing includes one or more of anhydrous ethanol, methanol, and water; And / or, the temperature of the drying is 80 - 100°C, and the time of the drying is 20 - 30 h.

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