Lithium ion battery conductive agent, preparation method and application thereof

Abstract

The application discloses a lithium ion battery conductive agent and a preparation method and application thereof, and belongs to the technical field of battery conductive agents.The application forms an efficient conductive network through the adhesion of elemental selenium on the surface of conductive carbon black and the synergistic effect of the conductive carbon black, significantly improves the overall conductive performance of the conductive agent, and is favorable for reducing the internal resistance of the battery.In addition, the elemental selenium can buffer the volume change in the charging and discharging process, reduces the structural damage of the electrode material, and meanwhile, the composite structure of the elemental selenium and the conductive carbon black is helpful to maintaining the integrity of the electrode, thereby prolonging the cycle life of the battery.In addition, the prepared lithium ion battery conductive agent is applied to the preparation of electrode sheets, and can effectively improve the electrochemical stability of the electrode under high-rate service conditions.

Description

Technical Field

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

[0002] Lithium-ion batteries, as the mainstream energy storage device, have been widely used in portable electronic devices, electric vehicles, and energy storage systems. With the rapid development of mobile internet and terminal hardware, and the increasing power of devices, higher demands are being placed on the energy density and power density of lithium-ion batteries. To balance high energy density and high power density while controlling manufacturing costs, electrode sheets are gradually developing towards thicker electrodes with high load and high compaction.

[0003] However, thick electrodes generally face problems such as decreased electrical performance and severe heat generation due to increased polarization during service. The core of these problems lies in the insufficient transport capacity of charge carriers (electrons and ions) inside the electrode, thus requiring the construction of an efficient conductive network within the electrode. Although the conductive agent accounts for a small proportion in the electrode powder (usually less than 5%, generally between 0.5% and 2%), its quality has a significant impact on the construction of the conductive network and the solid-liquid interface properties.

[0004] Currently, lithium-ion batteries primarily utilize carbon-based conductive agents, including carbon black, carbon nanotubes, graphene, and their composite systems. These traditional conductive agents only possess electronic conductivity and cannot directly conduct ionic electricity, although they can influence the ionic conductivity process to some extent by absorbing electrolyte. However, under conditions of high load and high compaction in thick electrodes, the electrolyte struggles to fully wet the electrode interior, severely hindering lithium-ion transport. To address these issues, some research has attempted to introduce solid electrolytes into thick electrodes to co-construct an electron-ion synergistic conductive network with the conductive agent. However, the addition of solid electrolyte particles increases the "breakpoints" in the electronic pathway, dilutes the electronically conductive phase, and causes insufficient interfacial contact between solid particles. Therefore, excessive addition of solid electrolyte can actually weaken the transmission efficiency of the electrode conductive network and degrade battery performance.

[0005] In conclusion, it is indeed necessary to provide a novel conductive agent that integrates electronic and ionic conductivity and can fill the interface in situ during the electrochemical reaction process, so as to effectively improve the quality of the conductive network in the thick electrode and thus enhance the performance of the thick electrode during service. Summary of the Invention

[0006] Based on this, in order to solve one of the aforementioned technical problems, the present invention provides a lithium-ion battery conductive agent, its preparation method, and its application. During battery formation and initial cycling, elemental selenium adhering to the surface of conductive carbon black can react in situ with the lithium source at the electrode / electrolyte interface to form interfacial phases such as lithium selenide, lithium selenide oxide, or LixSeOy. These interfacial phases can improve the interfacial contact between the conductive carbon black and the positive electrode active material, and regulate the local Li... + Migration environment reduces electrode polarization, thereby improving the capacity retention and cycle stability of thick electrodes under high-rate charge-discharge conditions.

[0007] The specific technical solution is as follows: A lithium-ion battery conductive agent, comprising conductive carbon black and elemental selenium attached to the conductive carbon black.

[0008] Furthermore, the conductive carbon black has a particle size of 20nm~120nm, a specific surface area of ​​50m² / g~300 m² / g, and an oil absorption value of 100~300 mL / 100 g.

[0009] Furthermore, the mass ratio of elemental selenium to conductive carbon black is (20~80):(20~80).

[0010] In addition, the present invention also provides a method for preparing a conductive agent for lithium-ion batteries, the method comprising the following steps: S1. The coarse selenium particles are ball-milled and sieved to obtain selenium powder; S2. Mix the selenium powder with conductive carbon black to obtain a mixture; S3. The mixture is heated under an inert atmosphere to allow elemental selenium to adhere to the conductive carbon black, and then cooled to obtain the lithium-ion battery conductive agent.

[0011] Further, in step S1, the particle size of the coarse selenium is 200~500μm; the ball milling speed is 300r / min~500r / min, and the time is 2~10h.

[0012] Furthermore, in step S1, the selenium powder is passed through a 300-800 mesh sieve.

[0013] Furthermore, in step S2, a ball mill is used for mixing, with a ball milling speed of 300 r / min to 800 r / min and a time of 1 to 6 hours.

[0014] Furthermore, in step S3, the heating temperature is 200~700℃, and the holding time is 1~8h.

[0015] In addition, the present invention also provides an application of the lithium-ion battery conductive agent, wherein the application is the application of the lithium-ion battery conductive agent in the preparation of electrode sheets.

[0016] Furthermore, the preparation of the electrode sheet includes the following steps: Polyvinylidene fluoride was added to N-methylpyrrolidone solvent to obtain a PVDF solution; The positive electrode active material, the lithium-ion battery conductive agent, and the PVDF solution are magnetically stirred until homogeneous, and the viscosity is adjusted to 1000~20000 cp.s to obtain the positive electrode slurry. The positive electrode slurry is uniformly coated on the surface of the aluminum foil current collector, and after drying, rolling to fix the thickness and cutting, an electrode sheet is obtained.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention, by attaching elemental selenium to the surface of conductive carbon black, achieves a synergistic effect with the conductive carbon black to form a highly efficient conductive network, significantly improving the overall conductivity of the conductive agent and helping to reduce the battery's internal resistance. Furthermore, elemental selenium can buffer volume changes during charge and discharge, reducing structural damage to the electrode material. Simultaneously, the composite structure of selenium and conductive carbon black helps maintain the integrity of the electrode, thereby extending the battery's cycle life.

[0018] 2. This invention employs a method of ball milling, mixing, and then heating to ensure uniform adhesion of elemental selenium to conductive carbon black. The process is simple, requires no complex equipment, and is easy to scale up for industrial production. By controlling parameters such as ball milling speed, time, sieve mesh size, heating temperature, and holding time, the microstructure and properties of the conductive agent can be precisely controlled. The overall cost is controllable, making it suitable for large-scale application.

[0019] 3. The lithium-ion battery conductive agent prepared by this invention has good compatibility with the positive electrode active material and binder. After drying, the electrode sheet thickness is uniform, which is beneficial to improving the production yield and electrochemical consistency of the electrode sheet. Moreover, the discharge specific capacity of the positive electrode is higher than that of the control positive electrode at all rates. The higher the rate, the greater the difference in capacity retention between the two, indicating that the conductive agent of this invention can effectively improve the electrochemical stability of the electrode under high-rate service conditions. Attached Figure Description

[0020] The invention will be further understood from the following description taken in conjunction with the accompanying drawings. The components in the drawings are not necessarily drawn to scale, but rather the emphasis is on illustrating the principles of the embodiments. In different views, the same reference numerals designate corresponding parts.

[0021] Figure 1 This is a comparison chart of the formation and rate performance of the control group and the experimental group in Example 1; Figure 2This is a comparison chart of the formation and rate performance of the control group and the experimental group in Example 2; Figure 3 This is a comparison chart of the formation and rate performance of the control group and the experimental group in Example 3; Figure 4 This is a comparison chart of the formation and rate performance of the control group and the experimental group in Example 4; Figure 5 This is a comparison chart of the formation and rate performance of the control group and the experimental group in Example 5; Figure 6 This is a comparison chart of the formation and rate performance of the control group and the experimental group in Example 6; Figure 7 This is a comparison chart of the formation and rate performance of the control group and the experimental group in Example 7; Figure 8 This is a comparison chart of the formation and rate performance of the control group and the experimental group in Example 8; Figure 9 This is a comparison chart of the formation and rate performance of the control group and the experimental group in Example 9; Figure 10 This is a comparison chart of the formation and rate performance of the control group and the experimental group in Example 10; Figure 11 Scanning electron microscope image of the original SP conductive carbon black; Figure 12 Scanning electron microscope image and EDS elemental distribution map of mechanically mixed Se / SP conductive carbon black sample; Figure 13 The images show scanning electron microscope (SEM) images, high-magnification scanning electron microscope (SEM) images, and EDS elemental distribution maps of the composite conductive agent obtained in Example 2. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to its embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of protection of the invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0024] One embodiment of the present invention provides a lithium-ion battery conductive agent, which includes conductive carbon black and elemental selenium attached to the conductive carbon black.

[0025] In one embodiment, the conductive carbon black has a particle size of 20nm~120nm, a specific surface area of ​​50m² / g~300 m² / g, and an oil absorption value of 100~300 mL / 100 g.

[0026] In one embodiment, the mass ratio of elemental selenium to conductive carbon black is (20~80):(20~80).

[0027] In addition, the present invention also provides a method for preparing a conductive agent for lithium-ion batteries, the method comprising the following steps: S1. The coarse selenium particles are ball-milled and sieved to obtain selenium powder; S2. Mix the selenium powder with conductive carbon black to obtain a mixture; S3. The mixture is heated under an inert atmosphere to allow elemental selenium to adhere to the conductive carbon black. After cooling, the conductive agent for lithium-ion batteries is obtained. The conductive agent of this invention undergoes highly uniform atomic layer deposition on the surface of nano-carbon black, resulting in uniform adhesion of elemental selenium to the conductive carbon black framework.

[0028] In one embodiment, in step S1, the particle size of the coarse selenium is 200~500μm; the ball milling speed is 300r / min~500r / min, and the time is 2~10h.

[0029] In one embodiment, in step S1, the selenium powder is passed through a 300-800 mesh sieve.

[0030] In one embodiment, in step S2, a ball mill is used for mixing, with a ball milling speed of 300 r / min to 800 r / min and a time of 1 to 6 hours.

[0031] In one embodiment, in step S3, the inert atmosphere is at least one of nitrogen, argon, and helium.

[0032] In one embodiment, in step S3, the heating temperature is 200~700℃ and the holding time is 1~8h.

[0033] In addition, the present invention also provides an application of the lithium-ion battery conductive agent, wherein the application is the application of the lithium-ion battery conductive agent in the preparation of electrode sheets.

[0034] In one embodiment, the preparation of the electrode sheet includes the following steps: Polyvinylidene fluoride was added to N-methylpyrrolidone solvent to obtain a PVDF solution; The positive electrode active material, the lithium-ion battery conductive agent, and the PVDF solution are magnetically stirred until homogeneous, and the viscosity is adjusted to 1000~20000 cp.s to obtain the positive electrode slurry. The positive electrode slurry is uniformly coated on the surface of the aluminum foil current collector, and after drying, rolling to fix the thickness and cutting, an electrode sheet is obtained.

[0035] In one embodiment, the process further includes the establishment of a composite conductive network: after assembling the electrode sheet containing selenium-coated carbon black obtained in step four with the negative electrode sheet, separator and electrolyte into a battery, a formation process is performed within a set voltage range; the formation process includes performing at least one charge-discharge cycle (preferably 2 to 5 cycles) with a small current, so that the elemental selenium attached to the surface of the selenium-coated carbon black undergoes a valence state transformation and reacts with lithium ions in an electrochemical process, thereby generating a lithium selenide phase in situ.

[0036] In one embodiment, the positive electrode active material is LiNi. x Co y Mn 1-x-y O2, 0.5≤x≤1.

[0037] In one embodiment, the drying temperature is 50~130°C.

[0038] In one embodiment, the areal capacity of the electrode sheet is 3.0~5.0 mAh / cm². 2 .

[0039] The conductive agent described above, by uniformly attaching elemental selenium onto conductive carbon black, possesses excellent conductivity, good cycle stability, and low preparation cost. Its preparation method is simple and controllable, has good compatibility with electrode paste, and produces uniform coating. At the same time, it is environmentally friendly and easy to promote industrialization.

[0040] The implementation schemes of the present invention will now be described in detail with reference to specific embodiments.

[0041] Example 1: Experimental group: Coarse selenium particles were fed into a ball mill and ball-milled at 300 r / min for 9 hours. The particles were then sieved through a 500-mesh sieve to obtain selenium powder with uniform particle size. The selenium powder and conductive carbon black were mixed at a predetermined mass ratio, wherein the mass percentage of selenium was 20%, and the mixture was ball-milled at a speed of 300 r / min for 5 hours to obtain the mixture. The mixture was placed in a ceramic boat and heated in a tube furnace under a nitrogen atmosphere at a temperature of 450°C for 4 hours, so that selenium was attached to the surface of the conductive carbon black SP skeleton in gaseous form. After cooling to room temperature, a lithium-ion battery conductive agent was obtained. Polyvinylidene fluoride (PVDF) was added to N-methylpyrrolidone to prepare a PVDF solution with a mass ratio of 10%. The lithium-ion battery conductive agent was then reacted with LiNi... 0.5 Co 0.2 Mn 0.3 O2 layered ternary cathode material (NCM523) and the above-mentioned PVDF solution are mixed, and LiNi 0.5 Co 0.2 Mn 0.3 The mass ratio of O2 layered ternary cathode material (NCM523), polyvinylidene fluoride, and lithium-ion battery conductive agent was 90:6:4. The mixture was stirred at 800 r / min for 8 h on a magnetic stirrer to obtain cathode slurry.

[0042] The positive electrode slurry is uniformly coated onto the surface of an aluminum foil current collector. After drying at 120°C to remove the solvent, the dried electrode sheet is rolled to a fixed thickness and cut into specified dimensions to obtain the thick positive electrode sheet of this embodiment. By controlling the solid content of the slurry, the coating amount, and the rolling thickness, the areal capacity of the positive electrode active material in the prepared positive electrode sheet is not less than 3.0 mAh / cm², preferably a thick electrode sheet with a high areal capacity of 3.0 mAh / cm², thus obtaining the positive electrode sheet.

[0043] The positive electrode, negative electrode, separator, and electrolyte are assembled into a bare cell according to the conventional lithium-ion battery manufacturing process. Then, the cell is packaged, injected with electrolyte, and sealed in sequence to obtain the positive electrode testing device.

[0044] The positive electrode testing device described in the above embodiment was placed in an environment of 25°C, and electrochemical tests were performed within a voltage range of 2.7-4.3V. First, it was charged with a current of 1 / 10 of its rated capacity and then discharged with a current of 1 / 10 of its rated capacity for three charge-discharge cycles to form a new electrode. The discharge specific capacity after formation stabilization was recorded to obtain the discharge specific capacity of the experimental group under 0.1C conditions. Within the voltage range of 2.7~4.3V, charge-discharge tests were performed sequentially at different rates: 0.1C, 0.2C, 0.5C, 1C, 2C, 3C, 4C, and 5C, with each rate cycled for 5 weeks to obtain the rate performance of the experimental group.

[0045] Control group: First, polyvinylidene fluoride (PVDF) was added to N-methylpyrrolidone to prepare a PVDF solution with a mass ratio of 10%. The positive electrode material, binder (PVDF), and conductive agent were mixed in a ratio of 90:6:4. The positive electrode material was a layered ternary positive electrode material of LiNi0.5Co0.2Mn0.3O2 (NCM523), and the conductive agent was a conventional conductive carbon black that had not been treated with selenium. The mixed slurry was stirred on a magnetic stirrer at 800 r / min for 8 h to obtain the positive electrode slurry. The positive electrode slurry is uniformly coated onto the surface of an aluminum foil current collector. After drying at 120°C to remove the solvent, the dried electrode sheet is rolled to a fixed thickness and then cut into specified dimensions. By controlling the solid content of the slurry, the coating amount, and the rolling thickness, the areal capacity of the positive electrode active material in the prepared positive electrode sheet is not less than 3.0 mAh / cm², preferably a thick electrode sheet with a high areal capacity of 3.0 mAh / cm², thus obtaining the positive electrode sheet. The positive electrode, negative electrode, separator, and electrolyte are assembled into a bare cell according to the conventional lithium-ion battery manufacturing process. Then, the cell is packaged, injected with electrolyte, and sealed in sequence to obtain the positive electrode testing device.

[0046] The control group's positive electrode testing device was placed at 25°C and electrochemical tests were performed within a voltage range of 2.7–4.3V. First, it was charged and discharged at 1 / 10 of its rated capacity current for three charge-discharge cycles. The discharge specific capacity after formation stabilization was recorded to obtain the control group's discharge specific capacity at 0.1C. Within the 2.7–4.3V voltage range, charge-discharge tests were performed sequentially at different rates: 0.1C, 0.2C, 0.5C, 1C, 2C, 3C, 4C, and 5C, with each rate cycled for 5 weeks to obtain the control group's rate performance.

[0047] Figure 1 This is a schematic diagram comparing the formation and rate performance of the experimental and control groups in Example 1. Figure 1 (a) Discharge specific capacity after 0.1C formation; (b) Schematic diagram of capacity retention rate changes during cycling at different rates at 0.1C. From Figure 1 As can be seen, after formation, the discharge specific capacity of the experimental group was higher than that of the control group, with an increase of 7.96%. During cycling at rates from 0.1 to 5C, the capacity retention rate of the experimental group was higher than that of the control group at all rates, and the difference in capacity retention rate increased with the higher the rate. This indicates that the experimental group using the conductive agent of this invention (conductive carbon black with attached elemental selenium) had a significantly higher discharge specific capacity after formation at 0.1C than the control group using conventional conductive carbon black. Furthermore, during cycling at different rates from 0.1C to 5C, the capacity retention rate of the experimental group was consistently better than that of the control group, and the difference became more pronounced with the higher the rate. This demonstrates that the conductive agent of this invention can effectively improve the initial discharge capacity and cycling stability of thick electrodes at high rates, and improve the synergistic conductivity of electrons and ions inside the electrode.

[0048] Example 2: Experimental group: Coarse selenium particles were fed into a ball mill and milled at 300 r / min for 9 hours. The particles were then sieved through a 500-mesh sieve to obtain selenium powder with uniform particle size. The selenium powder and conductive carbon black were mixed at a predetermined mass ratio, wherein the mass percentage of selenium was 40%, and the mixture was ball-milled at a speed of 300 r / min for 5 h to obtain the mixture. The mixture was placed in a ceramic boat and heated in a tube furnace under a nitrogen atmosphere at a temperature of 450°C for 4 hours, so that selenium was attached to the surface of the conductive carbon black SP skeleton in gaseous form. After cooling to room temperature, a composite conductive agent with selenium attached to conductive carbon black was obtained. Polyvinylidene fluoride (PVDF) powder was dissolved in NMP (N-methylpyrrolidone) solvent to prepare a 10% (w / w) PVDF solution. The resulting composite conductive agent was then reacted with LiNi. 0.5 Co 0.2 Mn 0.3 O2 layered ternary cathode material (NCM523) and the above-mentioned PVDF solution were mixed in a ratio of cathode material: binder: composite conductive agent = 90:6:4 to obtain a mixed slurry. The mixed slurry was stirred on a magnetic stirrer at 800 r / min for 8 h to obtain the cathode slurry.

[0049] The positive electrode slurry is uniformly coated onto the surface of an aluminum foil current collector. After drying at 120°C to remove the solvent, the dried electrode sheet is rolled to a fixed thickness and cut into specified dimensions to obtain the thick positive electrode sheet of this embodiment. By controlling the solid content of the slurry, the coating amount, and the rolling thickness, the areal capacity of the positive electrode active material in the prepared positive electrode sheet is not less than 3.0 mAh / cm², preferably a thick electrode sheet with a high areal capacity of 3.0 mAh / cm², thus obtaining the target positive electrode sheet.

[0050] Thick positive electrode sheets, negative electrode sheets, separators, and electrolytes are assembled into bare cells according to conventional lithium-ion battery manufacturing processes. Then, the cells are sequentially packaged, injected with electrolyte, and sealed to obtain a positive electrode testing device.

[0051] The control group's positive electrode testing device was placed at 25°C and electrochemical tests were performed within a voltage range of 2.7-4.3V. First, it was charged with a current of 1 / 10 of its rated capacity and then discharged with a current of 1 / 10 of its rated capacity for three charge-discharge cycles to form the experimental group. The discharge specific capacity after formation stabilization was recorded, yielding the discharge specific capacity of the experimental group at 0.1C. Within the 2.7–4.3V voltage range, charge-discharge tests were performed sequentially at different rates: 0.1C, 0.2C, 0.5C, 1C, 2C, 3C, 4C, and 5C, with each rate cycled for 5 weeks, to obtain the rate performance of the experimental group.

[0052] Control group: Polyvinylidene fluoride (PVDF) was added to N-methylpyrrolidone to prepare a PVDF solution with a mass ratio of 10%; the positive electrode material was mixed with binder and conductive agent at a ratio of 90:6:4, and the positive electrode material was LiNi.0.5 Co 0.2 Mn 0.3 O2 layered ternary cathode material (NCM523), the conductive agent is conventional conductive carbon black that has not been treated with selenium, the mixed slurry is stirred on a magnetic stirrer at 800 r / min for 8 h to obtain cathode slurry.

[0053] The positive electrode slurry is uniformly coated on the surface of the aluminum foil current collector. After drying to remove the solvent, the dried electrode sheet is rolled to a fixed thickness and cut into specified dimensions to obtain the thick positive electrode sheet of this embodiment. By controlling the solid content of the slurry, the coating amount, and the rolling thickness, the areal capacity of the positive electrode active material in the prepared positive electrode sheet is not less than 3.0 mAh / cm², preferably a thick electrode sheet with a high areal capacity of 3.0 mAh / cm², thus obtaining the target positive electrode.

[0054] Thick positive electrode sheets, negative electrode sheets, separators, and electrolytes are assembled into bare cells according to conventional lithium-ion battery manufacturing processes. Then, the cells are sequentially packaged, injected with electrolyte, and sealed to obtain a positive electrode testing device.

[0055] The positive electrode testing device of the control group was placed in an environment of 25°C and electrochemical tests were performed within a voltage range of 2.7-4.3V. First, it was charged with a current of 1 / 10 of its rated capacity and then discharged with a current of 1 / 10 of its rated capacity for three charge-discharge cycles to form a new electrode. The discharge specific capacity after formation stabilization was recorded to obtain the discharge specific capacity of the control group under 0.1C conditions. Within the voltage range of 2.7-4.3V, charge-discharge tests were performed sequentially at different rates of 0.1C, 0.2C, 0.5C, 1C, 2C, 3C, 4C, and 5C, with each rate cycled for 5 weeks to obtain the rate performance of the control group.

[0056] Figure 2 This is a schematic diagram comparing the formation and rate performance of the experimental and control groups in Example 2. Figure 2 (a) Discharge specific capacity after 0.1C formation; (b) Schematic diagram of capacity retention rate changes during cycling at different rates at 0.1C. From Figure 2 The results show that after formation, the average discharge specific capacity of the control group was 155.30±1.06 mAh / g, while that of the experimental group was 164.39±1.02 mAh / g, representing an increase of 5.85%. During cycling at rates from 0.1 to 5C, the capacity retention rate of the experimental group was higher than that of the control group at all rates. At the end of the 5C rate test, the capacity retention rate of the control group was 52.5%, while that of the experimental group reached 72.6%, indicating that the composite conductive agent exhibits better rate performance when the Se addition is around 40%~50%.

[0057] Example 3: Experimental group: Coarse selenium particles were fed into a ball mill and ball-milled at 300 r / min for 9 hours. The particles were then sieved through a 500-mesh sieve to obtain selenium powder with uniform particle size. The selenium powder and conductive carbon black were mixed at a predetermined mass ratio, wherein the mass percentage of selenium was 50%, and the mixture was ball-milled at a speed of 300 r / min for 5 hours to obtain the mixture. The mixture was placed in a ceramic boat and heated in a tube furnace under a nitrogen atmosphere at a temperature of 450°C for 4 hours, so that selenium was attached to the surface of the conductive carbon black SP skeleton in gaseous form. After cooling to room temperature, a composite conductive agent with selenium attached to conductive carbon black was obtained. Polyvinylidene fluoride (PVDF) was added to N-methylpyrrolidone to prepare a PVDF solution with a mass ratio of 10%; the resulting composite conductive agent was then reacted with LiNi... 0.5 Co 0.2 Mn 0.3 O2 layered ternary cathode material (NCM523) and the above-mentioned PVDF solution were mixed in a ratio of cathode material: binder: composite conductive agent = 90:6:4 to obtain a mixed slurry. The mixed slurry was stirred on a magnetic stirrer at 800 r / min for 8 h to obtain the cathode slurry.

[0058] The positive electrode slurry is uniformly coated on the surface of the aluminum foil current collector. After drying to remove the solvent, the dried electrode sheet is rolled to a fixed thickness and cut into specified dimensions to obtain the thick positive electrode sheet of this embodiment. By controlling the solid content of the slurry, the coating amount, and the rolling thickness, the areal capacity of the positive electrode active material in the prepared positive electrode sheet is not less than 3.0 mAh / cm², preferably a thick electrode sheet with a high areal capacity of 3.0 mAh / cm², thus obtaining the target positive electrode.

[0059] Thick positive electrode sheets, negative electrode sheets, separators, and electrolytes are assembled into bare cells according to conventional lithium-ion battery manufacturing processes. Then, the cells are sequentially packaged, injected with electrolyte, and sealed to obtain a positive electrode testing device.

[0060] The control group's positive electrode testing device was placed at 25°C and electrochemical tests were performed within a voltage range of 2.7-4.3V. First, it was charged with a current of 1 / 10 of its rated capacity and then discharged with a current of 1 / 10 of its rated capacity for three charge-discharge cycles to form the experimental group. The discharge specific capacity after formation stabilization was recorded, yielding the discharge specific capacity of the experimental group at 0.1C. Within the 2.7–4.3V voltage range, charge-discharge tests were performed sequentially at different rates: 0.1C, 0.2C, 0.5C, 1C, 2C, 3C, 4C, and 5C, with each rate cycled for 5 weeks, to obtain the rate performance of the experimental group.

[0061] Control group: Polyvinylidene fluoride (PVDF) was added to N-methylpyrrolidone to prepare a PVDF solution with a mass ratio of 10%; the positive electrode material was mixed with binder and conductive agent at a ratio of 90:6:4, and the positive electrode material was LiNi. 0.5 Co 0.2 Mn 0.3 O2 layered ternary cathode material (NCM523), the conductive agent is conventional conductive carbon black that has not been treated with selenium, the mixed slurry is stirred on a magnetic stirrer at 800 r / min for 8 h to obtain cathode slurry.

[0062] The positive electrode slurry is uniformly coated on the surface of the aluminum foil current collector. After drying to remove the solvent, the dried electrode sheet is rolled to a fixed thickness and cut into specified dimensions to obtain the thick positive electrode sheet of this embodiment. By controlling the solid content of the slurry, the coating amount, and the rolling thickness, the areal capacity of the positive electrode active material in the prepared positive electrode sheet is not less than 3.0 mAh / cm², preferably a thick electrode sheet with a high areal capacity of 3.0 mAh / cm², thus obtaining the target positive electrode.

[0063] Thick positive electrode sheets, negative electrode sheets, separators, and electrolytes are assembled into bare cells according to conventional lithium-ion battery manufacturing processes. Then, the cells are sequentially packaged, injected with electrolyte, and sealed to obtain a positive electrode testing device.

[0064] The control group's positive electrode testing device was placed at 25°C and electrochemical tests were performed within a voltage range of 2.7-4.3V. First, it was charged and discharged at 1 / 10 of its rated capacity current for three charge-discharge cycles to form the control group. The discharge specific capacity after formation stabilization was recorded, yielding the control group's discharge specific capacity at 0.1C. Within the 2.7-4.3V voltage range, charge-discharge tests were performed sequentially at different rates: 0.1C, 0.2C, 0.5C, 1C, 2C, 3C, 4C, and 5C, with each rate cycled for 5 weeks, yielding the control group's rate performance.

[0065] Figure 3 This is a schematic diagram comparing the formation and rate performance of the experimental and control groups in Example 3. Figure 3 (a) Discharge specific capacity after 0.1C formation; (b) Schematic diagram of capacity retention rate changes during cycling at different rates at 0.1C. From Figure 3The results show that after formation, the average discharge specific capacity of the control group was 155.45±1.01 mAh / g, while that of the experimental group was 165.01±1.06 mAh / g, representing an increase of 6.15%. During cycling at rates from 0.1 to 5C, the capacity retention rate of the experimental group was higher than that of the control group at all rates. At the end of the 5C rate test, the capacity retention rate of the control group was 52.9%, while that of the experimental group reached 71.5%, indicating that the composite conductive agent exhibits better rate performance when the Se addition is around 40%~50%.

[0066] Example 4: Experimental group: Coarse selenium particles were fed into a ball mill and milled at 300 r / min for 9 hours. The particles were then sieved through a 500-mesh sieve to obtain selenium powder with uniform particle size. The selenium powder and conductive carbon black were mixed at a predetermined mass ratio, wherein the mass percentage of selenium was 60%, and the mixture was ball-milled at a speed of 300 r / min for 5 hours to obtain the mixture. The mixture was placed in a ceramic boat and heated in a tube furnace under a nitrogen atmosphere at a temperature of 500°C for 4 hours, so that selenium was attached to the surface of the conductive carbon black SP skeleton in gaseous form. After cooling to room temperature, a composite conductive agent with selenium-attached conductive carbon black was obtained.

[0067] Polyvinylidene fluoride (PVDF) was added to N-methylpyrrolidone to prepare a PVDF solution with a mass ratio of 10%; the resulting composite conductive agent was then reacted with LiNi... 0.5 Co 0.2 Mn 0.3 O2 layered ternary cathode material (NCM523) and the above-mentioned PVDF solution were mixed in a ratio of cathode material: binder: composite conductive agent = 90:6:4 to obtain a mixed slurry. The mixed slurry was stirred on a magnetic stirrer at 800 r / min for 8 h to obtain the cathode slurry.

[0068] The positive electrode slurry is uniformly coated on the surface of the aluminum foil current collector. After drying to remove the solvent, the dried electrode sheet is rolled to a fixed thickness and cut into specified dimensions to obtain the thick positive electrode sheet of this embodiment. By controlling the solid content of the slurry, the coating amount, and the rolling thickness, the areal capacity of the positive electrode active material in the prepared positive electrode sheet is not less than 3.0 mAh / cm², preferably a thick electrode sheet with a high areal capacity of 3.0 mAh / cm², thus obtaining the target positive electrode.

[0069] Thick positive electrode sheets, negative electrode sheets, separators, and electrolytes are assembled into bare cells according to conventional lithium-ion battery manufacturing processes. Then, the cells are sequentially packaged, injected with electrolyte, and sealed to obtain a positive electrode testing device.

[0070] The control group's positive electrode testing device was placed at 25°C and electrochemical tests were performed within a voltage range of 2.7-4.3V. First, it was charged with a current of 1 / 10 of its rated capacity and then discharged with a current of 1 / 10 of its rated capacity for three charge-discharge cycles to form the experimental group. The discharge specific capacity after formation stabilization was recorded, yielding the discharge specific capacity of the experimental group at 0.1C. Within the 2.7–4.3V voltage range, charge-discharge tests were performed sequentially at different rates: 0.1C, 0.2C, 0.5C, 1C, 2C, 3C, 4C, and 5C, with each rate cycled for 5 weeks, to obtain the rate performance of the experimental group.

[0071] Control group: Polyvinylidene fluoride was added to N-methylpyrrolidone to prepare a PVDF solution with a mass ratio of 10%. The positive electrode material, binder, and conductive agent were mixed in a ratio of 90:6:4. The positive electrode material was LiNi0.5Co0.2Mn0.3O2 layered ternary positive electrode material (NCM523), and the conductive agent was conventional conductive carbon black that had not been treated with selenium. The mixed slurry was stirred at 800 r / min for 8 h on a magnetic stirrer to obtain the positive electrode slurry.

[0072] The positive electrode slurry is uniformly coated on the surface of the aluminum foil current collector. After drying to remove the solvent, the dried electrode sheet is rolled to a fixed thickness and cut into specified dimensions to obtain the thick positive electrode sheet of this embodiment. By controlling the solid content of the slurry, the coating amount, and the rolling thickness, the areal capacity of the positive electrode active material in the prepared positive electrode sheet is not less than 3.0 mAh / cm², preferably a thick electrode sheet with a high areal capacity of 3.0 mAh / cm², thus obtaining the target positive electrode.

[0073] Thick positive electrode sheets, negative electrode sheets, separators, and electrolytes are assembled into bare cells according to conventional lithium-ion battery manufacturing processes. Then, the cells are sequentially packaged, injected with electrolyte, and sealed to obtain a positive electrode testing device.

[0074] The positive electrode testing device of the control group was placed in an environment of 25°C and electrochemical tests were performed within a voltage range of 2.7-4.3V. First, it was charged with a current of 1 / 10 of its rated capacity and then discharged with a current of 1 / 10 of its rated capacity for three charge-discharge cycles to form a new electrode. The discharge specific capacity after formation stabilization was recorded to obtain the discharge specific capacity of the control group under 0.1C conditions. Within the voltage range of 2.7-4.3V, charge-discharge tests were performed sequentially at different rates of 0.1C, 0.2C, 0.5C, 1C, 2C, 3C, 4C, and 5C, with each rate cycled for 5 weeks to obtain the rate performance of the control group.

[0075] Figure 4 This is a schematic diagram comparing the formation and rate performance of the experimental and control groups in Example 4. Figure 4(a) Discharge specific capacity after 0.1C formation; (b) Schematic diagram of capacity retention rate changes during cycling at different rates at 0.1C. From Figure 4 The results show that after formation, the average discharge specific capacity of the control group was 155.07±0.98 mAh / g, while that of the experimental group was 163.01±0.99 mAh / g, representing an increase of 5.12%. During cycling at rates from 0.1 to 5C, the capacity retention rate of the experimental group was higher than that of the control group at all rates; at the end of the 5C rate test, the capacity retention rate of the control group was 51.8%, while that of the experimental group was 69.3%.

[0076] Example 5: Experimental group: Coarse selenium particles were fed into a ball mill and milled at 300 r / min for 9 hours. The particles were then sieved through a 500-mesh sieve to obtain selenium powder with uniform particle size. The selenium powder and conductive carbon black were mixed at a predetermined mass ratio, wherein the mass percentage of selenium was 80%, and the mixture was ball-milled at a speed of 300 r / min for 5 hours to obtain the mixture. The mixture was placed in a ceramic boat and heated in a tube furnace under a nitrogen atmosphere at a temperature of 450°C for 4 hours, so that selenium was attached to the surface of the conductive carbon black SP skeleton in gaseous form. After cooling to room temperature, a composite conductive agent with selenium-attached conductive carbon black was obtained.

[0077] Polyvinylidene fluoride (PVDF) was added to N-methylpyrrolidone to prepare a PVDF solution with a mass ratio of 10%; the resulting composite conductive agent was then reacted with LiNi... 0.5 Co 0.2 Mn 0.3 O2 layered ternary cathode material (NCM523) and the above-mentioned PVDF solution were mixed in a ratio of cathode material: binder: composite conductive agent = 90:6:4 to obtain a mixed slurry. The mixed slurry was stirred on a magnetic stirrer at 800 r / min for 8 h to obtain the cathode slurry.

[0078] The positive electrode slurry is uniformly coated on the surface of the aluminum foil current collector. After drying to remove the solvent, the dried electrode sheet is rolled to a fixed thickness and cut into specified dimensions to obtain the thick positive electrode sheet of this embodiment. By controlling the solid content of the slurry, the coating amount, and the rolling thickness, the areal capacity of the positive electrode active material in the prepared positive electrode sheet is not less than 3.0 mAh / cm², preferably a thick electrode sheet with a high areal capacity of 3.0 mAh / cm², thus obtaining the target positive electrode.

[0079] Thick positive electrode sheets, negative electrode sheets, separators, and electrolytes are assembled into bare cells according to conventional lithium-ion battery manufacturing processes. Then, the cells are sequentially packaged, injected with electrolyte, and sealed to obtain a positive electrode testing device.

[0080] The control group's positive electrode testing device was placed at 25°C and electrochemical tests were performed within a voltage range of 2.7-4.3V. First, it was charged with a current of 1 / 10 of its rated capacity and then discharged with a current of 1 / 10 of its rated capacity for three charge-discharge cycles to form the experimental group. The discharge specific capacity after formation stabilization was recorded, yielding the discharge specific capacity of the experimental group at 0.1C. Within the 2.7–4.3V voltage range, charge-discharge tests were performed sequentially at different rates: 0.1C, 0.2C, 0.5C, 1C, 2C, 3C, 4C, and 5C, with each rate cycled for 5 weeks, to obtain the rate performance of the experimental group.

[0081] Control group: Polyvinylidene fluoride was added to N-methylpyrrolidone to prepare a PVDF solution with a mass ratio of 10%. The positive electrode material, binder, and conductive agent were mixed in a ratio of 90:6:4. The positive electrode material was LiNi0.5Co0.2Mn0.3O2 layered ternary positive electrode material (NCM523), and the conductive agent was conventional conductive carbon black that had not been treated with selenium. The mixed slurry was stirred at 800 r / min for 8 h on a magnetic stirrer to obtain the positive electrode slurry.

[0082] The positive electrode slurry is uniformly coated on the surface of the aluminum foil current collector. After drying to remove the solvent, the dried electrode sheet is rolled to a fixed thickness and cut into specified dimensions to obtain the thick positive electrode sheet of this embodiment. By controlling the solid content of the slurry, the coating amount, and the rolling thickness, the areal capacity of the positive electrode active material in the prepared positive electrode sheet is not less than 3.0 mAh / cm², preferably a thick electrode sheet with a high areal capacity of 3.0 mAh / cm², thus obtaining the target positive electrode.

[0083] Thick positive electrode sheets, negative electrode sheets, separators, and electrolytes are assembled into bare cells according to conventional lithium-ion battery manufacturing processes. Then, the cells are sequentially packaged, injected with electrolyte, and sealed to obtain a positive electrode testing device.

[0084] The positive electrode testing device of the control group was placed in an environment of 25°C and electrochemical tests were performed within a voltage range of 2.7-4.3V. First, it was charged with a current of 1 / 10 of its rated capacity and then discharged with a current of 1 / 10 of its rated capacity for three charge-discharge cycles to form a new electrode. The discharge specific capacity after formation stabilization was recorded to obtain the discharge specific capacity of the control group under 0.1C conditions. Within the voltage range of 2.7-4.3V, charge-discharge tests were performed sequentially at different rates of 0.1C, 0.2C, 0.5C, 1C, 2C, 3C, 4C, and 5C, with each rate cycled for 5 weeks to obtain the rate performance of the control group.

[0085] Figure 5 This is a schematic diagram comparing the formation and rate performance of the experimental and control groups in Example 6. Figure 5 (a) Discharge specific capacity after 0.1C formation; (b) Schematic diagram of capacity retention rate changes during cycling at different rates at 0.1C. From Figure 5 As can be seen, after formation, the average discharge specific capacity of the control group was 155.43±0.99 mAh / g, while that of the experimental group was 160.80±1.04 mAh / g, representing an increase of 3.45%. During cycling at rates from 0.1 to 5C, the capacity retention rate of the experimental group was still higher than that of the control group at all rates. However, at the end of the 5C rate test, the capacity retention rate of the experimental group was 64.8%, which was significantly lower than that of the examples with Se addition of 40% and 50%. This indicates that when the Se addition was increased to 80%, an excess phenomenon occurred, and the performance of the composite conductive agent actually declined.

[0086] Example 6: Experimental group: Coarse selenium particles were fed into a ball mill and ball-milled at 300 r / min for 9 hours. The particles were then sieved through a 300-mesh sieve to obtain selenium powder with uniform particle size. The selenium powder and conductive carbon black were mixed at a predetermined mass ratio, wherein the mass percentage of selenium was 40%, and the mixture was ball-milled at a speed of 300 r / min for 5 h to obtain the mixture. The mixture was placed in a ceramic boat and heated in a tube furnace under a nitrogen atmosphere at a temperature of 450°C for 4 hours, so that selenium was attached to the surface of the conductive carbon black SP skeleton in gaseous form. After cooling to room temperature, a composite conductive agent with selenium-attached conductive carbon black was obtained.

[0087] Polyvinylidene fluoride (PVDF) was added to N-methylpyrrolidone to prepare a PVDF solution with a mass ratio of 10%; the resulting composite conductive agent was then reacted with LiNi... 0.5 Co 0.2 Mn 0.3 O2 layered ternary cathode material (NCM523) and the above-mentioned PVDF solution were mixed in a ratio of cathode material: binder: composite conductive agent = 90:6:4 to obtain a mixed slurry. The mixed slurry was stirred on a magnetic stirrer at 800 r / min for 8 h to obtain the cathode slurry.

[0088] The positive electrode slurry is uniformly coated on the surface of the aluminum foil current collector. After drying to remove the solvent, the dried electrode sheet is rolled to a fixed thickness and cut into specified dimensions to obtain the thick positive electrode sheet of this embodiment. By controlling the solid content of the slurry, the coating amount, and the rolling thickness, the areal capacity of the positive electrode active material in the prepared positive electrode sheet is not less than 3.0 mAh / cm², preferably a thick electrode sheet with a high areal capacity of 3.0 mAh / cm², thus obtaining the target positive electrode.

[0089] Thick positive electrode sheets, negative electrode sheets, separators, and electrolytes are assembled into bare cells according to conventional lithium-ion battery manufacturing processes. Then, the cells are sequentially packaged, injected with electrolyte, and sealed to obtain a positive electrode testing device.

[0090] The control group's positive electrode testing device was placed at 25°C and electrochemical tests were performed within a voltage range of 2.7-4.3V. First, it was charged with a current of 1 / 10 of its rated capacity and then discharged with a current of 1 / 10 of its rated capacity for three charge-discharge cycles to form the experimental group. The discharge specific capacity after formation stabilization was recorded, yielding the discharge specific capacity of the experimental group at 0.1C. Within the 2.7–4.3V voltage range, charge-discharge tests were performed sequentially at different rates: 0.1C, 0.2C, 0.5C, 1C, 2C, 3C, 4C, and 5C, with each rate cycled for 5 weeks, to obtain the rate performance of the experimental group.

[0091] Control group: Polyvinylidene fluoride was added to N-methylpyrrolidone to prepare a PVDF solution with a mass ratio of 10%. The positive electrode material, binder, and conductive agent were mixed in a ratio of 90:6:4. The positive electrode material was LiNi0.5Co0.2Mn0.3O2 layered ternary positive electrode material (NCM523), and the conductive agent was conventional conductive carbon black that had not been treated with selenium. The mixed slurry was stirred at 800 r / min for 8 h on a magnetic stirrer to obtain the positive electrode slurry.

[0092] The positive electrode slurry is uniformly coated on the surface of the aluminum foil current collector. After drying to remove the solvent, the dried electrode sheet is rolled to a fixed thickness and cut into specified dimensions to obtain the thick positive electrode sheet of this embodiment. By controlling the solid content of the slurry, the coating amount, and the rolling thickness, the areal capacity of the positive electrode active material in the prepared positive electrode sheet is not less than 3.0 mAh / cm², preferably a thick electrode sheet with a high areal capacity of 3.0 mAh / cm², thus obtaining the target positive electrode.

[0093] Thick positive electrode sheets, negative electrode sheets, separators, and electrolytes are assembled into bare cells according to conventional lithium-ion battery manufacturing processes. Then, the cells are sequentially packaged, injected with electrolyte, and sealed to obtain a positive electrode testing device.

[0094] The positive electrode testing device of the control group was placed in an environment of 25°C and electrochemical tests were performed within a voltage range of 2.7-4.3V. First, it was charged with a current of 1 / 10 of its rated capacity and then discharged with a current of 1 / 10 of its rated capacity for three charge-discharge cycles to form a new electrode. The discharge specific capacity after formation stabilization was recorded to obtain the discharge specific capacity of the control group under 0.1C conditions. Within the voltage range of 2.7-4.3V, charge-discharge tests were performed sequentially at different rates of 0.1C, 0.2C, 0.5C, 1C, 2C, 3C, 4C, and 5C, with each rate cycled for 5 weeks to obtain the rate performance of the control group.

[0095] Figure 6 This is a schematic diagram comparing the formation and rate performance of the experimental and control groups in Example 6. Figure 6 (a) Discharge specific capacity after 0.1C formation; (b) Schematic diagram of capacity retention rate changes during cycling at different rates at 0.1C. From Figure 6 As can be seen, after formation, the average discharge specific capacity of the control group was 155.19±1.02 mAh / g, while that of the experimental group was 161.99±0.99 mAh / g, representing an increase of 4.38%. During cycling at rates from 0.1 to 5C, the capacity retention rate of the experimental group at the end of the 5C test was 65.6%, which was higher than that of the control group but lower than that of the example under the 700-mesh sieve condition. This indicates that the Se particle size is too coarse under the 300-mesh condition, which is not conducive to the formation of a more uniform composite structure on the conductive carbon black surface.

[0096] Example 7: Experimental group: Coarse selenium particles were fed into a ball mill and milled at 300 r / min for 9 hours. The mixture was then sieved through a 700-mesh sieve to obtain selenium powder with uniform particle size. The selenium powder and conductive carbon black were mixed at a predetermined mass ratio, wherein the mass percentage of selenium was 40%, and the mixture was ball-milled at a speed of 300 r / min for 5 h to obtain the mixture. The mixture was placed in a ceramic boat and heated in a tube furnace under a nitrogen atmosphere at a temperature of 450°C for 4 hours, so that selenium was attached to the surface of the conductive carbon black SP skeleton in gaseous form. After cooling to room temperature, a composite conductive agent with selenium-attached conductive carbon black was obtained.

[0097] Polyvinylidene fluoride (PVDF) was added to N-methylpyrrolidone to prepare a PVDF solution with a mass ratio of 10%; the resulting composite conductive agent was then reacted with LiNi... 0.5 Co 0.2 Mn 0.3 O2 layered ternary cathode material (NCM523) and the above-mentioned PVDF solution were mixed in a ratio of cathode material: binder: composite conductive agent = 90:6:4 to obtain a mixed slurry. The mixed slurry was stirred on a magnetic stirrer at 800 r / min for 8 h to obtain the cathode slurry.

[0098] The positive electrode slurry is uniformly coated on the surface of the aluminum foil current collector. After drying to remove the solvent, the dried electrode sheet is rolled to a fixed thickness and cut into specified dimensions to obtain the thick positive electrode sheet of this embodiment. By controlling the solid content of the slurry, the coating amount, and the rolling thickness, the areal capacity of the positive electrode active material in the prepared positive electrode sheet is not less than 3.0 mAh / cm², preferably a thick electrode sheet with a high areal capacity of 3.0 mAh / cm², thus obtaining the target positive electrode.

[0099] Thick positive electrode sheets, negative electrode sheets, separators, and electrolytes are assembled into bare cells according to conventional lithium-ion battery manufacturing processes. Then, the cells are sequentially packaged, injected with electrolyte, and sealed to obtain a positive electrode testing device.

[0100] The control group's positive electrode testing device was placed at 25°C and electrochemical tests were performed within a voltage range of 2.7-4.3V. First, it was charged with a current of 1 / 10 of its rated capacity and then discharged with a current of 1 / 10 of its rated capacity for three charge-discharge cycles to form the experimental group. The discharge specific capacity after formation stabilization was recorded, yielding the discharge specific capacity of the experimental group at 0.1C. Within the 2.7–4.3V voltage range, charge-discharge tests were performed sequentially at different rates: 0.1C, 0.2C, 0.5C, 1C, 2C, 3C, 4C, and 5C, with each rate cycled for 5 weeks, to obtain the rate performance of the experimental group.

[0101] Control group: Polyvinylidene fluoride was added to N-methylpyrrolidone to prepare a PVDF solution with a mass ratio of 10%. The positive electrode material, binder, and conductive agent were mixed in a ratio of 90:6:4. The positive electrode material was LiNi0.5Co0.2Mn0.3O2 layered ternary positive electrode material (NCM523), and the conductive agent was conventional conductive carbon black that had not been treated with selenium. The mixed slurry was stirred at 800 r / min for 8 h on a magnetic stirrer to obtain the positive electrode slurry.

[0102] The positive electrode slurry is uniformly coated on the surface of the aluminum foil current collector. After drying to remove the solvent, the dried electrode sheet is rolled to a fixed thickness and cut into specified dimensions to obtain the thick positive electrode sheet of this embodiment. By controlling the solid content of the slurry, the coating amount, and the rolling thickness, the areal capacity of the positive electrode active material in the prepared positive electrode sheet is not less than 3.0 mAh / cm², preferably a thick electrode sheet with a high areal capacity of 3.0 mAh / cm², thus obtaining the target positive electrode.

[0103] Thick positive electrode sheets, negative electrode sheets, separators, and electrolytes are assembled into bare cells according to conventional lithium-ion battery manufacturing processes. Then, the cells are sequentially packaged, injected with electrolyte, and sealed to obtain a positive electrode testing device.

[0104] The positive electrode testing device of the control group was placed in an environment of 25°C and electrochemical tests were performed within a voltage range of 2.7-4.3V. First, it was charged with a current of 1 / 10 of its rated capacity and then discharged with a current of 1 / 10 of its rated capacity for three charge-discharge cycles to form a new electrode. The discharge specific capacity after formation stabilization was recorded to obtain the discharge specific capacity of the control group under 0.1C conditions. Within the voltage range of 2.7-4.3V, charge-discharge tests were performed sequentially at different rates of 0.1C, 0.2C, 0.5C, 1C, 2C, 3C, 4C, and 5C, with each rate cycled for 5 weeks to obtain the rate performance of the control group.

[0105] Figure 7 This is a schematic diagram comparing the formation and rate performance of the experimental and control groups in Example 7. Figure 7 (a) Discharge specific capacity after 0.1C formation; (b) Schematic diagram of capacity retention rate changes during cycling at different rates at 0.1C. From Figure 7 As can be seen, after formation, the average discharge specific capacity of the control group was 155.60±1.06 mAh / g, while that of the experimental group was 164.16±1.04 mAh / g, representing an increase of 5.50%. During cycling at rates from 0.1 to 5C, the experimental group maintained a capacity retention rate of 71.1% at the end of the 5C test, which was higher than that of the example under 300-mesh sieving conditions. This indicates that the Se particle size after 700-mesh sieving is more suitable for forming a more uniform adhesion layer on the surface of the conductive carbon black skeleton.

[0106] Example 8: Experimental group: Coarse selenium particles were fed into a ball mill and milled at 300 r / min for 9 hours. The particles were then sieved through a 500-mesh sieve to obtain selenium powder with uniform particle size. The selenium powder and conductive carbon black were mixed at a predetermined mass ratio, wherein the mass percentage of selenium was 40%, and the mixture was ball-milled at a speed of 300 r / min for 5 h to obtain the mixture. The mixture was placed in a ceramic boat and heated in a tube furnace under a nitrogen atmosphere at a temperature of 450°C for 2 hours, so that selenium was attached to the surface of the conductive carbon black SP skeleton in gaseous form. After cooling to room temperature, a composite conductive agent with selenium-attached conductive carbon black was obtained.

[0107] Polyvinylidene fluoride (PVDF) was added to N-methylpyrrolidone to prepare a PVDF solution with a mass ratio of 10%; the resulting composite conductive agent was then reacted with LiNi... 0.5 Co 0.2 Mn 0.3O2 layered ternary cathode material (NCM523) and the above-mentioned PVDF solution were mixed in a ratio of cathode material: binder: composite conductive agent = 90:6:4 to obtain a mixed slurry. The mixed slurry was stirred on a magnetic stirrer at 800 r / min for 8 h to obtain the cathode slurry.

[0108] The positive electrode slurry is uniformly coated on the surface of the aluminum foil current collector. After drying to remove the solvent, the dried electrode sheet is rolled to a fixed thickness and cut into specified dimensions to obtain the thick positive electrode sheet of this embodiment. By controlling the solid content of the slurry, the coating amount, and the rolling thickness, the areal capacity of the positive electrode active material in the prepared positive electrode sheet is not less than 3.0 mAh / cm², preferably a thick electrode sheet with a high areal capacity of 3.0 mAh / cm², thus obtaining the target positive electrode.

[0109] Thick positive electrode sheets, negative electrode sheets, separators, and electrolytes are assembled into bare cells according to conventional lithium-ion battery manufacturing processes. Then, the cells are sequentially packaged, injected with electrolyte, and sealed to obtain a positive electrode testing device.

[0110] The control group's positive electrode testing device was placed at 25°C and electrochemical tests were performed within a voltage range of 2.7-4.3V. First, it was charged with a current of 1 / 10 of its rated capacity and then discharged with a current of 1 / 10 of its rated capacity for three charge-discharge cycles to form the experimental group. The discharge specific capacity after formation stabilization was recorded, yielding the discharge specific capacity of the experimental group at 0.1C. Within the 2.7–4.3V voltage range, charge-discharge tests were performed sequentially at different rates: 0.1C, 0.2C, 0.5C, 1C, 2C, 3C, 4C, and 5C, with each rate cycled for 5 weeks, to obtain the rate performance of the experimental group.

[0111] Control group: Polyvinylidene fluoride was added to N-methylpyrrolidone to prepare a PVDF solution with a mass ratio of 10%. The positive electrode material, binder, and conductive agent were mixed in a ratio of 90:6:4. The positive electrode material was LiNi0.5Co0.2Mn0.3O2 layered ternary positive electrode material (NCM523), and the conductive agent was conventional conductive carbon black that had not been treated with selenium. The mixed slurry was stirred at 800 r / min for 8 h on a magnetic stirrer to obtain the positive electrode slurry.

[0112] The positive electrode slurry is uniformly coated on the surface of the aluminum foil current collector. After drying to remove the solvent, the dried electrode sheet is rolled to a fixed thickness and cut into specified dimensions to obtain the thick positive electrode sheet of this embodiment. By controlling the solid content of the slurry, the coating amount, and the rolling thickness, the areal capacity of the positive electrode active material in the prepared positive electrode sheet is not less than 3.0 mAh / cm², preferably a thick electrode sheet with a high areal capacity of 3.0 mAh / cm², thus obtaining the target positive electrode.

[0113] Thick positive electrode sheets, negative electrode sheets, separators, and electrolytes are assembled into bare cells according to conventional lithium-ion battery manufacturing processes. Then, the cells are sequentially packaged, injected with electrolyte, and sealed to obtain a positive electrode testing device.

[0114] The positive electrode testing device of the control group was placed in an environment of 25°C and electrochemical tests were performed within a voltage range of 2.7-4.3V. First, it was charged with a current of 1 / 10 of its rated capacity and then discharged with a current of 1 / 10 of its rated capacity for three charge-discharge cycles to form a new electrode. The discharge specific capacity after formation stabilization was recorded to obtain the discharge specific capacity of the control group under 0.1C conditions. Within the voltage range of 2.7-4.3V, charge-discharge tests were performed sequentially at different rates of 0.1C, 0.2C, 0.5C, 1C, 2C, 3C, 4C, and 5C, with each rate cycled for 5 weeks to obtain the rate performance of the control group.

[0115] Figure 8 This is a schematic diagram comparing the formation and rate performance of the experimental and control groups in Example 8. Figure 8 (a) Discharge specific capacity after 0.1C formation; (b) Schematic diagram of capacity retention rate changes during cycling at different rates at 0.1C. From Figure 8 As can be seen, after formation, the average discharge specific capacity of the control group was 154.98±1.02 mAh / g, while that of the experimental group was 162.21±1.00 mAh / g, representing an increase of 4.67%. During cycling at rates from 0.1 to 5C, the experimental group maintained a capacity retention rate of 67.8% at the end of the 5C test, indicating that the composite conductive agent had a certain improvement effect when the heat preservation time was only 2 hours, but the overall performance was slightly lower than that of the example with heat preservation for 4 hours.

[0116] Example 9: Experimental group: Coarse selenium particles were fed into a ball mill and ball-milled at 300 r / min for 9 hours. The particles were then sieved through a 500-mesh sieve to obtain selenium powder with uniform particle size. The selenium powder and conductive carbon black were mixed at a predetermined mass ratio, wherein the mass percentage of selenium was 40%, and the mixture was ball-milled at a speed of 300 r / min for 5 h to obtain the mixture. The mixture was placed in a ceramic boat and heated in a tube furnace under a nitrogen atmosphere at a temperature of 450°C for 6 hours, so that selenium was attached to the surface of the conductive carbon black SP skeleton in gaseous form. After cooling to room temperature, a composite conductive agent with selenium-attached conductive carbon black was obtained.

[0117] Polyvinylidene fluoride (PVDF) was added to N-methylpyrrolidone to prepare a PVDF solution with a mass ratio of 10%; the resulting composite conductive agent was then reacted with LiNi... 0.5 Co0.2 Mn 0.3 O2 layered ternary cathode material (NCM523) and the above-mentioned PVDF solution were mixed in a ratio of cathode material: binder: composite conductive agent = 90:6:4 to obtain a mixed slurry. The mixed slurry was stirred on a magnetic stirrer at 800 r / min for 8 h to obtain the cathode slurry.

[0118] The positive electrode slurry is uniformly coated on the surface of the aluminum foil current collector. After drying to remove the solvent, the dried electrode sheet is rolled to a fixed thickness and cut into specified dimensions to obtain the thick positive electrode sheet of this embodiment. By controlling the solid content of the slurry, the coating amount, and the rolling thickness, the areal capacity of the positive electrode active material in the prepared positive electrode sheet is not less than 3.0 mAh / cm², preferably a thick electrode sheet with a high areal capacity of 3.0 mAh / cm², thus obtaining the target positive electrode.

[0119] Thick positive electrode sheets, negative electrode sheets, separators, and electrolytes are assembled into bare cells according to conventional lithium-ion battery manufacturing processes. Then, the cells are sequentially packaged, injected with electrolyte, and sealed to obtain a positive electrode testing device.

[0120] The control group's positive electrode testing device was placed at 25°C and electrochemical tests were performed within a voltage range of 2.7-4.3V. First, it was charged with a current of 1 / 10 of its rated capacity and then discharged with a current of 1 / 10 of its rated capacity for three charge-discharge cycles to form the experimental group. The discharge specific capacity after formation stabilization was recorded, yielding the discharge specific capacity of the experimental group at 0.1C. Within the 2.7–4.3V voltage range, charge-discharge tests were performed sequentially at different rates: 0.1C, 0.2C, 0.5C, 1C, 2C, 3C, 4C, and 5C, with each rate cycled for 5 weeks, to obtain the rate performance of the experimental group.

[0121] Control group: Polyvinylidene fluoride was added to N-methylpyrrolidone to prepare a PVDF solution with a mass ratio of 10%. The positive electrode material, binder, and conductive agent were mixed in a ratio of 90:6:4. The positive electrode material was LiNi0.5Co0.2Mn0.3O2 layered ternary positive electrode material (NCM523), and the conductive agent was conventional conductive carbon black that had not been treated with selenium. The mixed slurry was stirred at 800 r / min for 8 h on a magnetic stirrer to obtain the positive electrode slurry.

[0122] The positive electrode slurry is uniformly coated on the surface of the aluminum foil current collector. After drying to remove the solvent, the dried electrode sheet is rolled to a fixed thickness and cut into specified dimensions to obtain the thick positive electrode sheet of this embodiment. By controlling the solid content of the slurry, the coating amount, and the rolling thickness, the areal capacity of the positive electrode active material in the prepared positive electrode sheet is not less than 3.0 mAh / cm², preferably a thick electrode sheet with a high areal capacity of 3.0 mAh / cm², thus obtaining the target positive electrode.

[0123] Thick positive electrode sheets, negative electrode sheets, separators, and electrolytes are assembled into bare cells according to conventional lithium-ion battery manufacturing processes. Then, the cells are sequentially packaged, injected with electrolyte, and sealed to obtain a positive electrode testing device.

[0124] The positive electrode testing device of the control group was placed in an environment of 25°C and electrochemical tests were performed within a voltage range of 2.7-4.3V. First, it was charged with a current of 1 / 10 of its rated capacity and then discharged with a current of 1 / 10 of its rated capacity for three charge-discharge cycles to form a new electrode. The discharge specific capacity after formation stabilization was recorded to obtain the discharge specific capacity of the control group under 0.1C conditions. Within the voltage range of 2.7-4.3V, charge-discharge tests were performed sequentially at different rates of 0.1C, 0.2C, 0.5C, 1C, 2C, 3C, 4C, and 5C, with each rate cycled for 5 weeks to obtain the rate performance of the control group.

[0125] Figure 9 This is a schematic diagram comparing the formation and rate performance of the experimental and control groups in Example 9. Figure 9 (a) Discharge specific capacity after 0.1C formation; (b) Schematic diagram of capacity retention rate changes during cycling at different rates at 0.1C. From Figure 9 As can be seen, after formation, the average discharge specific capacity of the control group was 155.33±1.01 mAh / g, while that of the experimental group was 161.16±1.00 mAh / g, representing an increase of 3.75%. During cycling at rates from 0.1 to 5C, the capacity retention rate of the experimental group at the end of the 5C test was 65.4%, which was lower than that of the 4h heat preservation example. This indicates that when the heat preservation time was extended to 6h, some Se in the atmosphere was volatilized or carried out, resulting in a decrease in overall performance.

[0126] Example 10: Experimental group: Coarse selenium particles were fed into a ball mill and milled at 300 r / min for 9 hours. The particles were then sieved through a 500-mesh sieve to obtain selenium powder with uniform particle size. The selenium powder and conductive carbon black were mixed at a predetermined mass ratio, wherein the mass percentage of selenium was 40%, and the mixture was ball-milled at a speed of 300 r / min for 5 h to obtain the mixture. The mixture was placed in a ceramic boat and heated in a tube furnace under a nitrogen atmosphere at a temperature of 450°C for 8 hours, so that selenium was attached to the surface of the conductive carbon black SP skeleton in gaseous form. After cooling to room temperature, a composite conductive agent with selenium-attached conductive carbon black was obtained.

[0127] Polyvinylidene fluoride (PVDF) was added to N-methylpyrrolidone (NMP) to prepare a PVDF solution with a mass ratio of 10%. The resulting composite conductive agent was mixed with LiNi0.5Co0.2Mn0.3O2 layered ternary cathode material (NCM523) and the above PVDF solution in a ratio of cathode material: binder: composite conductive agent = 90:6:4 to obtain a mixed slurry. The mixed slurry was stirred on a magnetic stirrer at 800 r / min for 8 h to obtain the cathode slurry.

[0128] The positive electrode slurry is uniformly coated on the surface of the aluminum foil current collector. After drying to remove the solvent, the dried electrode sheet is rolled to a fixed thickness and cut into specified dimensions to obtain the thick positive electrode sheet of this embodiment. By controlling the solid content of the slurry, the coating amount, and the rolling thickness, the areal capacity of the positive electrode active material in the prepared positive electrode sheet is not less than 3.0 mAh / cm², preferably a thick electrode sheet with a high areal capacity of 3.0 mAh / cm², thus obtaining the target positive electrode.

[0129] Thick positive electrode sheets, negative electrode sheets, separators, and electrolytes are assembled into bare cells according to conventional lithium-ion battery manufacturing processes. Then, the cells are sequentially packaged, injected with electrolyte, and sealed to obtain a positive electrode testing device.

[0130] The control group's positive electrode testing device was placed at 25°C and electrochemical tests were performed within a voltage range of 2.7-4.3V. First, it was charged with a current of 1 / 10 of its rated capacity and then discharged with a current of 1 / 10 of its rated capacity for three charge-discharge cycles to form the experimental group. The discharge specific capacity after formation stabilization was recorded, yielding the discharge specific capacity of the experimental group at 0.1C. Within the 2.7–4.3V voltage range, charge-discharge tests were performed sequentially at different rates: 0.1C, 0.2C, 0.5C, 1C, 2C, 3C, 4C, and 5C, with each rate cycled for 5 weeks, to obtain the rate performance of the experimental group.

[0131] Control group: Polyvinylidene fluoride was added to N-methylpyrrolidone to prepare a PVDF solution with a mass ratio of 10%. The positive electrode material, binder, and conductive agent were mixed in a ratio of 90:6:4. The positive electrode material was LiNi0.5Co0.2Mn0.3O2 layered ternary positive electrode material (NCM523), and the conductive agent was conventional conductive carbon black that had not been treated with selenium. The mixed slurry was stirred at 800 r / min for 8 h on a magnetic stirrer to obtain the positive electrode slurry.

[0132] The positive electrode slurry is uniformly coated on the surface of the aluminum foil current collector. After drying to remove the solvent, the dried electrode sheet is rolled to a fixed thickness and cut into specified dimensions to obtain the thick positive electrode sheet of this embodiment. By controlling the solid content of the slurry, the coating amount, and the rolling thickness, the areal capacity of the positive electrode active material in the prepared positive electrode sheet is not less than 3.0 mAh / cm², preferably a thick electrode sheet with a high areal capacity of 3.0 mAh / cm², thus obtaining the target positive electrode.

[0133] Thick positive electrode sheets, negative electrode sheets, separators, and electrolytes are assembled into bare cells according to conventional lithium-ion battery manufacturing processes. Then, the cells are sequentially packaged, injected with electrolyte, and sealed to obtain a positive electrode testing device.

[0134] The positive electrode testing device of the control group was placed in an environment of 25°C and electrochemical tests were performed within a voltage range of 2.7-4.3V. First, it was charged with a current of 1 / 10 of its rated capacity and then discharged with a current of 1 / 10 of its rated capacity for three charge-discharge cycles to form a new electrode. The discharge specific capacity after formation stabilization was recorded to obtain the discharge specific capacity of the control group under 0.1C conditions. Within the voltage range of 2.7-4.3V, charge-discharge tests were performed sequentially at different rates of 0.1C, 0.2C, 0.5C, 1C, 2C, 3C, 4C, and 5C, with each rate cycled for 5 weeks to obtain the rate performance of the control group.

[0135] Figure 10 This is a schematic diagram comparing the formation and rate performance of the experimental and control groups in Example 10. Figure 10 (a) Discharge specific capacity after 0.1C formation; (b) Schematic diagram of capacity retention rate changes during cycling at different rates at 0.1C. From Figure 10 The results show that after formation, the average discharge specific capacity of the control group was 155.14±0.72 mAh / g, while that of the experimental group was 156.30±0.81 mAh / g, representing an increase of 0.75%. During cycling at rates from 0.1 to 5C, the capacity retention rate of the experimental group at the end of the 5C test was 53.9%, which is close to the 51.9% of the control group. This indicates that when the holding time was extended to 8 hours, Se further volatilized or was carried out, and the gain effect of the composite conductive agent basically disappeared.

[0136] In addition, the following experiments were conducted to further demonstrate the technical solution of the present invention: To further illustrate the microstructural characteristics of the composite conductive agent of this application, scanning electron microscopy and EDS elemental distribution characterization were performed on the original SP conductive carbon black, the mechanically mixed Se / SP conductive carbon black sample, and the composite conductive agent obtained in Example 2. The results show that there are significant differences in the morphology and Se distribution of the samples under different preparation methods.

[0137] Figure 11 This is a scanning electron microscope image of the original SP conductive carbon black, from... Figure 11 It is evident that the original SP conductive carbon black exhibits a relatively typical chain-like agglomeration structure, with particles interconnected to form a continuous conductive framework.

[0138] Figure 12 Scanning electron microscope (SEM) images and EDS elemental distribution maps of mechanically mixed Se / SP conductive carbon black samples are shown. (a) Low-magnification SEM image of the mechanically mixed Se / SP conductive carbon black sample; (b) High-magnification SEM image of the mechanically mixed Se / SP conductive carbon black sample; (c) C elemental distribution map of the mechanically mixed Se / SP conductive carbon black sample; (d) Se elemental distribution map of the mechanically mixed Se / SP conductive carbon black sample. Figure 12 It is evident that the mechanically mixed Se / SP conductive carbon black sample is still dominated by the conductive carbon black skeleton. The Se element is discretely distributed in the sample and exhibits local enrichment, indicating that simple mechanical mixing is insufficient to achieve uniform and stable dispersion of Se on the conductive carbon black surface.

[0139] Figure 13 The images show scanning electron microscope (SEM) images, high-magnification SEM images, and EDS elemental distribution maps of the composite conductive agent obtained in Example 2: (a) Low-magnification SEM image of the mechanically mixed Se / SP conductive carbon black sample; (b) High-magnification SEM image of the mechanically mixed Se / SP conductive carbon black sample; (c) C elemental distribution map of the mechanically mixed Se / SP conductive carbon black sample; (d) Se elemental distribution map of the mechanically mixed Se / SP conductive carbon black sample. Figure 13 As can be seen, the composite conductive agent obtained in Example 2 still maintains the original skeleton structure of conductive carbon black. The distribution of Se element in the sample is more uniform, and the local enrichment phenomenon is weakened. This indicates that after heat treatment, Se can be more uniformly attached to the surface of SP conductive carbon black, thereby forming a more stable composite conductive agent structure.

[0140] Based on the electrochemical test results of Example 2, it can be seen that the composite conductive agent is superior to the control group in terms of discharge specific capacity and high rate capacity retention, indicating that the uniformly composite Se / SP conductive carbon black structure is beneficial to improving the quality of the conductive network in the thick electrode and enhancing the rate performance.

[0141] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0142] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A lithium-ion battery conductive agent, characterized in that, The lithium-ion battery conductive agent includes conductive carbon black and elemental selenium attached to the conductive carbon black.

2. The lithium-ion battery conductive agent of claim 1, wherein, The conductive carbon black has a particle size of 20nm~120nm, a specific surface area of ​​50m² / g~300 m² / g, and an oil absorption value of 100~300 mL / 100 g.

3. The lithium-ion battery conductive agent of claim 1, wherein, The mass ratio of elemental selenium to conductive carbon black is (20~80):(20~80).

4. A method of preparing a lithium ion battery conductive agent, characterized by, The preparation method is used to prepare the lithium-ion battery conductive agent according to any one of claims 1 to 3, and the preparation method includes the following steps: S1. The coarse selenium particles are ball-milled and sieved to obtain selenium powder; S2. Mix the selenium powder with conductive carbon black to obtain a mixture; S3. The mixture is heated under an inert atmosphere to allow elemental selenium to adhere to the conductive carbon black, and then cooled to obtain the lithium-ion battery conductive agent.

5. The preparation method according to claim 4, characterized in that, In step S1, the particle size of the coarse selenium is 200~500μm; the ball milling speed is 300r / min~500r / min, and the time is 2~10h.

6. The preparation method according to claim 4, characterized in that, In step S1, the selenium powder is passed through a 300-800 mesh sieve.

7. The preparation method according to claim 4, characterized in that, In step S2, a ball mill is used for mixing. The ball milling speed is 300 r / min to 800 r / min, and the time is 1 to 6 hours.

8. The preparation method according to claim 4, characterized in that, In step S3, the heating temperature is 200~700℃, and the holding time is 1~8h.

9. Use of a lithium ion battery conductive agent, characterized in that, The application is the use of the lithium-ion battery conductive agent according to any one of claims 1 to 3 in the preparation of electrode sheets.

10. Use according to claim 9, characterized in that, The preparation of the electrode sheet includes the following steps: Polyvinylidene fluoride was added to N-methylpyrrolidone solvent to obtain a PVDF solution; The positive electrode active material, the lithium-ion battery conductive agent according to claims 1 to 3, and the PVDF solution are magnetically stirred until homogeneous, and the viscosity is adjusted to 1000 to 20000 cp.s to obtain a positive electrode slurry; The positive electrode slurry is uniformly coated on the surface of the aluminum foil current collector, and after drying, rolling to fix the thickness and cutting, an electrode sheet is obtained.

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