Positive electrode material coated with graphene and carbon nanotube composite conductive agent and preparation method and application of positive electrode material

Abstract

The invention provides a graphene and carbon nanotube composite conductive agent coated positive electrode material and a preparation method and application thereof, and belongs to the technical field of battery materials. The positive electrode material is prepared through an integrated process of liquid phase pre-dispersion and spray drying, and a three-dimensional interpenetrating conductive network in which graphene (a two-dimensional conductive surface) and carbon nanotubes (a one-dimensional conductive bridge) are synergistic is constructed. According to the preparation method adopted by the invention, GN and c-MWCNTs in the positive electrode material are uniformly dispersed at a molecular level in EMD, a stable three-dimensional conductive network is constructed, a voltage platform of a battery assembled by using the positive electrode material is slow in attenuation, an LED can be ensured to maintain high brightness for a longer time, and the positive electrode material has excellent structural stability under long-term intermittent use.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, specifically to a cathode material coated with a graphene and carbon nanotube composite conductive agent, its preparation method, and its application. More specifically, it provides a high-performance cathode modification material for lithium manganese primary batteries, particularly a manganese dioxide cathode material based on co-coating with a graphene and carbon nanotube composite conductive agent and suitable for luminescent electron bleaching needle batteries. Background Technology

[0002] As a special type of fishing gear, luminous electronic floats require their built-in needle-type lithium manganese batteries (such as CR425, CR322, CR316, etc.) to operate in harsh environments involving humidity, vibration, and long-term intermittent low-current discharge (driving LED flashing). This necessitates that the battery possess extremely low internal resistance, a high and stable operating voltage platform, and excellent intermittent cycle life.

[0003] Traditional needle-type lithium manganese battery cathodes primarily employ a physical mixture of electrolytic manganese dioxide (EMD) and conductive agents such as acetylene black. However, acetylene black provides point-like contact, requiring a large addition amount (typically >4%) to construct an effective conductive network, sacrificing energy density. Furthermore, it has limited buffering capacity against volumetric strain caused by the Jahn-Teller effect during discharge, leading to electrode pulverization, increased contact resistance, and impacting long-term use. Graphene (GN) possesses ultra-high specific surface area and surface conductivity, while carbon nanotubes (CNTs) exhibit high aspect ratio and linear conductivity. GN alone is prone to stacking, and CNTs alone are prone to agglomeration; simple physical mixing of the two fails to achieve optimal synergy. Current technologies often employ dry mixing or conventional liquid-phase mixing for electrode materials, resulting in insufficient dispersion uniformity and a lack of systematic material design and performance verification systems specifically addressing the pulse discharge characteristics of phosphorescent batteries.

[0004] Therefore, a complete technical solution has been developed that enables GN and CNTs to achieve molecular-level uniform dispersion in EMD, construct a stable three-dimensional conductive network, and is equipped with scientific and repeatable characterization methods to verify its applicability to the special working conditions of luminous drift. This solution has an urgent industrial demand. Summary of the Invention

[0005] To address the problems of poor dispersion uniformity and insufficient performance of phosphorescent batteries caused by graphene and carbon nanotubes as conductive agents in the preparation of electrode materials in existing technologies, this invention provides a cathode material coated with a graphene-carbon nanotube composite conductive agent, its preparation method, and its application. The cathode material is prepared through an integrated process of liquid-phase pre-dispersion and spray drying, constructing a three-dimensional interpenetrating conductive network in which graphene (two-dimensional conductive surface) and carbon nanotubes (one-dimensional conductive bridge) work synergistically. This improves the dispersion uniformity of graphene and carbon nanotubes in the cathode material and optimizes the electronic conductivity and intermittent cycle life of the cathode material, thereby enhancing the battery's superior structural stability and low internal resistance under long-term intermittent use.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: In a first aspect, a cathode material coated with a graphene-carbon nanotube composite conductive agent is provided, comprising a manganese dioxide matrix and a composite conductive agent coated on the surface of the manganese dioxide matrix, wherein the composite conductive agent comprises graphene and carboxylated multi-walled carbon nanotubes. In some embodiments, the surface of the EMD particles in the cathode material is covered with a wrinkled GN film, and numerous c-MWCNTs are interwoven and connected between the particles like "steel bars," forming an ideal three-dimensional network.

[0007] In some embodiments, the mass ratio of graphene to carboxylated multi-walled carbon nanotubes is (1~3):(1~3), preferably 1:1, 1:2, 1:3, 2:3, 3:2, 3:1, 2:1, and any two of the above values ​​constitute any range.

[0008] In some embodiments, the mass ratio of the manganese dioxide matrix to the composite conductive agent is (96~99):(1~4), preferably 96:4, 97:3, 98:2, 99:1, or any two of the above values ​​forming any range.

[0009] In some embodiments, the composite conductive agent accounts for 1 to 5 wt% of the total mass of the positive electrode material, preferably 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, or any two of the above values ​​forming any range.

[0010] In a first aspect, a method for preparing a cathode material coated with a graphene and carbon nanotube composite conductive agent is provided, comprising: S1: Carboxylated multi-walled carbon nanotubes and the first dispersant are dispersed in the first solvent and subjected to ultrasonic treatment to obtain suspension A; S2: Graphene and the second dispersant are dispersed in the second solvent and subjected to high-speed shearing to obtain suspension B; S3: Mix suspension A and suspension B, and sonicate to obtain composite conductive agent suspension C; S4: Manganese dioxide powder is slowly added to suspension C under stirring, while ultrasonic dispersion is used for continuous compounding to obtain a uniform slurry D; S5: Pump slurry D into a centrifugal spray drying tower, control the feed rate, inlet temperature and outlet temperature to obtain composite microsphere precursor E; S6: The precursor E is placed in a tube furnace and heat-treated under nitrogen protection. After natural cooling, it is sieved to obtain the cathode material F.

[0011] In some embodiments, the first dispersant and the second dispersant are sodium dodecylbenzenesulfonate. In some embodiments, the first solvent and the second solvent are at least one of deionized water and ethanol.

[0012] In some embodiments, the mass ratio of the carboxylated multi-walled carbon nanotubes to the first dispersant is (1~3):1, preferably 1:1, 1:2, 1:3, or any two of the above values ​​forming any range.

[0013] In some embodiments, the ultrasonic treatment in S1 lasts for 30 to 60 minutes, and the power is 600 to 800 W. In some embodiments, the ultrasonic treatment uses an ultrasonic cell disruptor.

[0014] In some embodiments, the mass ratio of graphene to the second dispersant is (1~3):1, preferably 1:1, 1:2, 1:3, or any two of the above values ​​forming any range.

[0015] In some embodiments, the high-speed shearing process in S2 lasts for 10 to 20 minutes, and the rotation speed is 8000 to 10000 rpm. In some embodiments, the high-speed shearing is performed using a high-speed shear emulsifier.

[0016] In some embodiments, the ultrasonic treatment in S3 lasts for 10 to 20 minutes, and preferably has a power of 600 to 800 W. In some embodiments, the ultrasonic treatment is performed using an ultrasonic cell disruptor.

[0017] In some embodiments, the stirring speed in S4 is 500-1000 rpm, the ultrasonic power is 300-500 W, and the compounding time is 50-80 minutes. In some embodiments, the ultrasonic-assisted dispersion is achieved using an ultrasonic probe.

[0018] In some embodiments, the feed rate in S5 is 15~20 mL / min, the inlet temperature is 200~230℃, and the outlet temperature is 90~100℃.

[0019] In some embodiments, the heat treatment temperature in S6 is 280~320°C, and the time is 1~5 hours.

[0020] In some embodiments, S1-S4 are processed at room temperature. In this invention, "room temperature" refers to room temperature of 10~40℃, preferably 20~30℃ or 25℃.

[0021] Thirdly, the present invention provides an application of the cathode material described herein in an energy storage device.

[0022] In some embodiments, the energy storage device is a luminous electronic bleaching needle battery or a lithium manganese primary battery. In some embodiments, the battery is a needle-type battery (such as CR425, CR322, CR316, etc.) used for luminous bleaching.

[0023] Fourthly, a preparation system for preparing the cathode material of the present invention is provided, comprising a pre-dispersion module, a liquid-phase composite reactor with an ultrasonic device, a centrifugal spray drying tower, and an inert atmosphere heat treatment furnace.

[0024] Fifthly, a systematic characterization method for the cathode material described in this invention is provided, comprising: (1) Morphology and structure characterization: Field emission scanning electron microscopy (FE-SEM) was used to observe the micromorphology of the material and the distribution of GN / CNTs; X-ray diffraction (XRD) was used to analyze the crystal structure of the material; Raman spectroscopy was used to analyze the defect degree and coupling state of the carbon material. (2) Physical performance characterization: The electronic conductivity of the electrode material after tableting was measured using a four-probe powder resistivity tester; (3) Electrochemical performance characterization: The positive electrode material was made into a CR2032 coin cell experimental cell. The Blue Battery Test System was used to perform constant current discharge, pulse discharge and intermittent cycle tests, and the voltage-capacity curve, voltage-time curve and capacity retention data were recorded.

[0025] In some embodiments, the pulse discharge test regime in the electrochemical performance characterization is as follows: constant current discharge at a rate of 0.2C for 10 seconds, followed by rest for 50 seconds as one cycle, until the cutoff voltage is 2.0V.

[0026] Beneficial effects: This invention provides a method for preparing a cathode material coated with a graphene and carbon nanotube composite conductive agent. The method combines chemically modified CNTs (i.e., using c-MWCNTs) with physical dispersion (ultrasonic treatment / high-speed shearing) to fully deagglomerate GN and c-MWCNTs in water, followed by pre-coupling through ultrasonic treatment. Subsequently, it is composited with EMD particles in the liquid phase. Utilizing the instantaneous curing effect of spray drying, GN sheets are "wrapped" on the EMD surface. Simultaneously, the fibrous properties of CNTs "bridge" different EMD particles and GN sheets, forming a stable three-dimensional conductive and mechanical support network with interpenetrating "surface-line" structures (e.g., ...). Figure 1 As shown in the figure, the positive electrode material was obtained.

[0027] The cathode material structure prepared by this invention can greatly improve electron transport efficiency and buffer the volume change of EMD, giving the cathode material extremely low internal resistance, a high and stable operating voltage platform, and excellent intermittent cycle life. The preparation method used in this invention enables GN and c-MWCNTs in the cathode material to achieve molecular-level uniform dispersion in EMD, constructing a stable three-dimensional conductive network. The battery assembled using this structure experiences slow voltage platform decay, ensuring that the LED maintains high brightness for a longer period of time and exhibits excellent structural stability under long-term intermittent use.

[0028] This invention provides a complete physicochemical and electrochemical performance characterization scheme for materials, including the use of scanning electron microscopy, a four-probe tester, and a blue battery testing system. Specific data and charts demonstrate that when the total doping amount is 2.0 wt%, the material can significantly reduce the electrode internal resistance by >60%, improve the pulse discharge voltage plateau and cycle stability of the battery, and is particularly suitable for the long-term and stable operation requirements of luminous bleaching needle batteries.

[0029] This invention successfully developed a high-performance lithium-manganese battery cathode material coated with a GN / CNT composite conductive agent through innovative material design, scalable fabrication processes, and systematic characterization methods. The fabrication method is environmentally friendly, efficient, and easy to produce continuously. The accompanying characterization methods comprehensively verify the invention from microstructure, crystal structure, and macroscopic conductivity to the final battery's simulated electrochemical performance, providing a complete data chain and fully demonstrating the effectiveness, reliability, and innovation of the invention. Attached Figure Description

[0030] Figure 1 Figure 1 shows a comparison of SEM images of the cathode material prepared in Example 1 and the conventional cathode material prepared in Comparative Example 1. Figure (a) shows the conventional cathode material prepared in Comparative Example 1, and Figure (b) shows the cathode material prepared in Example 1.

[0031] Figure 2 The image shows a comparison of the Raman spectra of the cathode material prepared in Example 1 and the cathode material prepared in Comparative Example 2.

[0032] Figure 3 A comparison of the 0.2C constant current discharge curves of coin cells assembled with the cathode material prepared in Example 1 and the cathode material prepared in Comparative Example 1.

[0033] Figure 4 A comparison of pulse discharge voltage-time curves for batteries 1 and 2 during simulated nighttime light drift operation (partial magnification shows a single pulse).

[0034] Figure 5 This is a comparison chart of the capacity retention rates of battery 1 and battery 2 after 100 pulse cycles.

[0035] The present invention will be further illustrated below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Detailed Implementation

[0036] The present invention will be further illustrated below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0037] I. Chemicals and Instruments Electrolytic manganese dioxide (Xiangtan Electrochemical HEMD, 200~325 mesh); graphene (GN, specific surface area ~500m²). 2 / g); carboxylated multi-walled carbon nanotubes (c-MWCNTs, diameter 7-15 nm, length 10-50 μm); dispersant sodium dodecylbenzenesulfonate (SDBS); deionized water freshly prepared.

[0038] Ultrasonic cell disruptor (Ningbo Xinzhi, JY92-IIDN); high-speed shear emulsifier (Shanghai Fluke, FA25); centrifugal spray drying tower (Wuxi Linzhou, LZ-2.5); field emission scanning electron microscope (FE-SEM, Zeiss Sigma 300); Raman spectrometer (Renishaw inVia, laser wavelength 532nm); four-probe powder resistivity meter (Guangzhou four-probe, RTS-9); LAND battery testing system (LAND CT3001A); centrifugal spray drying tower (Wuxi Linzhou, LZ-2.5).

[0039] Preparation General Examples: A method for preparing a positive electrode material coated with a graphene and carbon nanotube composite conductive agent includes: (1) Take carboxylated multi-walled carbon nanotubes (c-MWCNTs) and sodium dodecylbenzenesulfonate (SDBS) and add them to deionized water. Then treat them with an ultrasonic cell disruptor for 30-60 minutes (power 600W) to obtain suspension A; (2) Add GN and sodium dodecylbenzenesulfonate (SDBS) to deionized water and treat with a high-speed shear emulsifier for 10-20 minutes (10000 rpm) to obtain suspension B; (3) Mix suspension A and suspension B, and sonicate for 10-20 minutes to obtain composite conductive agent suspension C; (4) Electrolytic manganese dioxide (EMD) powder is slowly added to suspension C under stirring (500 rpm), while the ultrasonic probe (300W) is turned on to assist dispersion. The mixture is continuously compounded for 50-80 minutes to obtain a uniform slurry D. (5) Pump slurry D into a centrifugal spray drying tower, control the feed rate to 15~20 mL / min, the inlet temperature to 200~230℃, and the outlet temperature to 90~100℃ to obtain composite microsphere precursor E; (6) Place the precursor E in a tube furnace and heat-treat it at 280~320℃ for 1~5 hours under nitrogen protection. After natural cooling, sieve it through a 200-mesh sieve to obtain the final cathode material F.

[0040] Table 1 Preparation parameters The preparation parameters for Examples 6-8 are the same as those for Example 1 in Table 1, except that the ratio of c-MWCNTs and GN is different. The rest are the same as those for Example 1. See Table 2 below for details.

[0041] Table 2 Material Change Parameters Comparative Example 1 (Traditional cathode material) 960g of EMD and 40g of acetylene black (AB) were dry-mixed in a high-speed mixer for 2 hours to obtain a control sample.

[0042] Comparative Example 2 Precursor E was obtained by mixing GN, c-MWCNTs, SDBS, and EMD powders according to the parameters of Example 1. 0 After heat treatment and natural cooling, the material is sieved through a 400-mesh sieve to obtain the final cathode material F. 0 .

[0043] Example of Results: Systematic Characterization and Electrochemical Performance Testing All tests were conducted at a constant temperature of 25°C.

[0044] I. Morphology and Structure Characterization (Principle: To verify whether the microstructure of the material conforms to the design) 1. The microstructure of the cathode material prepared in Example 1 of this invention and the conventional cathode material prepared in Comparative Example 1 were verified using field emission scanning electron microscopy. The results are as follows: Figure 1 As shown.

[0045] Result: As Figure 1 As shown in (a), in the conventional cathode material prepared in Comparative Example 1, acetylene black adheres to the EMD surface in particulate form, resulting in insufficient contact. Figure 1 As shown in (b), in the cathode material prepared in Example 1, the surface of the EMD particles is covered with a layer of wrinkled GN film, and many c-MWCNTs are interwoven and connected between the particles like "steel bars", forming an ideal three-dimensional network.

[0046] 2. The microstructure of the cathode material prepared in Example 1 and the cathode material prepared in Comparative Example 2 was verified using Raman spectroscopy at a laser wavelength of 532 nm. The results are as follows: Figure 2 As shown.

[0047] Result: As Figure 2 As shown, compared to the physically mixed GN+c-MWCNTs powder in Comparative Example 2, the D peak (~1350 cm⁻¹) of the cathode material prepared in Example 1 is significantly higher. -1 (representing defects / edges) and G peak (~1580 cm⁻¹) -1 , representing graphitized sp 2 The change in the intensity ratio (ID / IG) of GN indicates that during the preparation process, the π-π bonds of GN and c-MWCNTs were coupled, forming a tighter conductive network rather than a simple stack.

[0048] 3. The positive electrode material prepared in the embodiments of the present invention and the positive electrode material prepared in Comparative Example 1 were pressed into standard discs under the same pressure (10 MPa), and their volume resistivity was measured using a four-probe powder resistivity tester. The results are shown in Table 3.

[0049] Table 3 Volume Resistivity Results: As shown in Table 3, with the conductive agent dosage reduced by half, the electronic conductivity of the standard disc of the cathode material prepared in the embodiments of the present invention is significantly better than that of Comparative Example 1. The formation of a highly efficient conductive network with less conductive agent indicates that the effective coating of the matrix material and the conductive agent results in better interfacial contact, smoother electron transport paths, lower interfacial resistance, and reduced interfacial side reactions. Compared with Examples 12 and 13, which use a single conductive agent component, Examples 1-11 of the present invention, which use dual conductive agents, exhibit better synergistic effects. Example 10, a cathode material with a total conductive agent doping amount of 1 wt%, showed limited improvement in internal resistance reduction performance; Example 11, a cathode material with a total composite conductive agent doping amount of 4 wt%, further reduced internal resistance, but decreased energy density and reduced cost-effectiveness. In the embodiments of the present invention, the standard disc of the cathode material prepared in Example 1 using a 1:1 mass ratio of GN / c-MWCNTs as the conductive agent exhibits the best volumetric conductivity.

[0050] II. Electrochemical Performance Characterization (Principle: Verifying Battery Performance by Simulating Real-World Application Scenarios) The positive electrode material prepared in Example 1 and the positive electrode material prepared in Comparative Example 1 were assembled with lithium foil negative electrode, separator and electrolyte to form CR2032 coin cells (corresponding to battery 1 and battery 2 respectively) for performance comparison test.

[0051] Instrument: LAND CT3001A battery testing system.

[0052] Test 1: Constant Current Discharge Performance Method: Discharge at a constant current of 0.2C (approximately 0.6mA) until the cutoff voltage of 2.0V.

[0053] The results are as follows Figure 3 As shown in Table 4.

[0054] Table 4 Performance Comparison Test From Table 4 and Figure 3 It can be seen that the operating voltage platform of battery 1 is significantly higher than that of battery 2, the average operating voltage is better than that of battery 2, and the discharge curve is more stable. This indicates that the battery prepared using the positive electrode material prepared in Example 1 of the present invention has less polarization, which shows that the scheme of the present invention has achieved success in optimizing material structure and reducing interfacial side reactions, which is beneficial to improving the intermittent cycle life of the battery.

[0055] Test 2: Pulse Discharge Performance (Core Test, Simulating Nighttime LED Flashing) The assembled batteries 1 and 2 in Test 1 were discharged at a rate of 0.2C for 10 seconds, followed by a rest period of 50 seconds as one pulse cycle, and cyclically repeated until the cutoff voltage of 2.0V was reached.

[0056] The results are as follows Figure 4 As shown, within a single pulse, battery 1 experiences a smaller voltage drop, and its voltage recovers faster and higher after resting. Throughout the discharge process, its voltage plateau decays slowly, ensuring that the LED maintains high brightness for a longer period.

[0057] Test 3: Intermittent Cycle Life Battery 1 and Battery 2 assembled in Test 1 were cycled at a 0.2C pulse regime (same as Test 2), and the discharge capacity was recorded every 100 pulses to examine the capacity retention rate.

[0058] The results are as follows Figure 5 As shown, after 300 pulse cycles, the capacity retention rate of battery 1 was 92.5%, while that of battery 2 was only 74.8%. This demonstrates that the battery prepared with the cathode material prepared in Example 1 of this invention has excellent structural stability under long-term intermittent use.

[0059] Industrial application The material preparation process and system provided by this invention can be directly adapted to existing lithium-manganese battery production lines. The characterization method provides a complete solution for standardized quality control and performance evaluation. The needle-type lithium-manganese battery manufactured based on the cathode material of this invention can significantly improve the battery life, brightness stability, and overall product lifespan, demonstrating clear market economic benefits.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A cathode material coated with a graphene and carbon nanotube composite conductive agent, characterized in that, It includes a manganese dioxide matrix and a composite conductive agent coated on the surface of the manganese dioxide matrix, wherein the composite conductive agent includes graphene and carboxylated multi-walled carbon nanotubes.

2. The cathode material according to claim 1, characterized in that, The mass ratio of graphene to carboxylated multi-walled carbon nanotubes is (1~3):(1~3).

3. The positive electrode material according to claim 1, characterized in that, The mass ratio of the manganese dioxide matrix to the composite conductive agent is (96~99):(1~4). Alternatively, the composite conductive agent accounts for 1 to 5 wt% of the total mass of the positive electrode material.

4. A method for preparing the cathode material according to any one of claims 1 to 3, characterized in that, include: S1: Carboxylated multi-walled carbon nanotubes and the first dispersant are dispersed in the first solvent and subjected to ultrasonic treatment to obtain suspension A; S2: Graphene and the second dispersant are dispersed in the second solvent and subjected to high-speed shearing to obtain suspension B; S3: Mix suspension A and suspension B, and sonicate to obtain composite conductive agent suspension C; S4: Manganese dioxide powder is slowly added to suspension C under stirring, while ultrasonic dispersion is used for continuous compounding to obtain a uniform slurry D; S5: Pump slurry D into a centrifugal spray drying tower, control the feed rate, inlet temperature and outlet temperature to obtain composite microsphere precursor E; S6: The precursor E is placed in a tube furnace and heat-treated under nitrogen protection. After natural cooling, it is sieved to obtain the cathode material F.

5. The preparation method according to claim 4, characterized in that, The first dispersant and the second dispersant are sodium dodecylbenzenesulfonate; the first solvent and the second solvent are at least one of deionized water and ethanol.

6. The preparation method according to claim 4, characterized in that, The mass ratio of the carboxylated multi-walled carbon nanotubes to the first dispersant is (1~3):1; The mass ratio of graphene to the second dispersant is (1~3):

1.

7. The preparation method according to claim 4, characterized in that, The ultrasonic treatment time in S1 is 30-60 minutes, and the power is 600-800W; the high-speed shearing treatment time in S2 is 10-20 minutes, and the rotation speed is 8000-10000 rpm. The ultrasonic treatment time in S3 is 10-20 minutes; The stirring speed in S4 is 500~1000 rpm, the ultrasonic power is 300~500 W, and the compounding time is 50~80 minutes.

8. The preparation method according to claim 4, characterized in that, The feed rate in S5 is 15~20 mL / min, the inlet temperature is 200~230℃, and the outlet temperature is 90~100℃. The heat treatment temperature in S6 is 280~320℃, and the time is 1~5 hours.

9. Use of the cathode material according to any one of claims 1 to 3 in an energy storage device.

10. The use according to claim 9, characterized in that, The energy storage device is a luminescent electronic bleaching needle battery or a lithium manganese primary battery.

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