An active slurry, a positive electrode sheet, and a preparation method and application thereof

Abstract

The application belongs to the technical field of energy storage, and particularly discloses an active slurry, a positive electrode sheet, a preparation method and application thereof. The active slurry comprises an active material and an organic solvent, and the solid content of the active slurry is 45wt%-60wt%. The raw material of the active material comprises, in terms of mass fraction, 93.5wt%-97.5wt% of an active substance, 1.5wt%-4.0wt% of a binder and 1.0wt%-2.5wt% of a conductive substance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of energy storage, and particularly relates to an active slurry, a positive electrode sheet and a preparation method and application thereof. BACKGROUND

[0002] Hybrid capacitors achieve high energy density and high power density energy storage through electric double-layer capacitance effect and Faraday reaction, and have wide application prospects. The working principle includes two main processes: on the one hand, ions undergo reversible adsorption and desorption process on the surface of electrochemically active materials; on the other hand, lithium ions participate in reversible Faraday chemical reaction in the bulk phase of electrode materials. Common hybrid capacitor electrode materials are usually high specific surface area carbon materials or conductive polymers, which store electric charge through electric double-layer effect; at the same time, active materials such as metal oxides or conductive polymers are added, so that the electrode can further store electric energy through chemical reaction, thereby improving the overall performance of the capacitor.

[0003] The design of the positive electrode material of the hybrid capacitor is particularly critical, which needs to have both high specific surface area capacitive active material (such as activated carbon) and battery active material (such as lithium nickel cobalt manganese oxide, lithium iron phosphate, etc.) capable of undergoing redox reaction with lithium ions. In the charging and discharging process, the capacitive active material relies on the adsorption and desorption process of electric charge to affect the energy characteristics of the capacitor, and the diffusion speed of lithium ions in the battery material determines its power characteristics. Therefore, optimizing the production process of the positive electrode sheet helps to improve the energy density and power density of the hybrid capacitor, meeting the development needs of the "double high" hybrid capacitor.

[0004] In the research field of hybrid capacitors, foreign technology is more advanced. Companies such as JM Energy in Japan and VINATech in South Korea have accumulated rich experience in the development of hybrid capacitor monomers, and are at the international leading level in material science, electrochemistry and engineering technology. The wide application of hybrid capacitors in the fields of transportation, industrial control and consumer electronics has further promoted the innovation and upgrading of positive electrode materials, and helped the research and development of high-performance hybrid capacitors.

[0005] In China, the technical research and industrialization of hybrid capacitors have made significant progress. Shanghai Aowei, Ningbo Zhongche and other companies have realized the large-scale production of hybrid capacitors, and the products are widely used in electric buses, solar energy storage and other fields. In addition, many universities and research institutions in China are also actively promoting the innovation of hybrid capacitor positive electrode materials. Zhejiang Normal University and Nanyang Technological University jointly developed a porous CoO / Co-Cu-S multi-stage tubular heterostructure material with a special pore structure, which showed excellent electrochemical performance and excellent rate performance and cycle stability, which provided a useful research idea for the development of high-performance electrode materials. In addition, the team of Dalian Institute of Chemical Physics of the Chinese Academy of Sciences developed a rocking chair type hybrid energy storage device with lithium ion battery characteristics using orthogonal phase Nb2O5 and high-nickel ternary material NCA as positive and negative electrodes, which successfully realized the hybrid capacitor of lithium ions shuttling between electrodes, and achieved high energy density and high power density. At a power density of 9.1kW / kg, an energy density of 83Wh / kg was obtained, which provided a new idea for the design of "double high" hybrid energy storage devices.

[0006] At present, the selection of positive electrode materials and the preparation process of electrode sheets are the key to improve the performance of hybrid capacitors. The current commercial positive electrode materials mainly focus on ternary materials and lithium iron phosphate technology, but single material cannot meet the demand of high energy and high power density, therefore it is urgent to develop a positive electrode preparation method combining the characteristics of battery and capacitor to meet the market demand for high-performance and low-cost hybrid capacitors. SUMMARY

[0007] The purpose of the present application is to solve the above problems, and provide an active slurry, a positive electrode sheet and a preparation method and application thereof.

[0008] In a first aspect, an active slurry adopts the following technical scheme:

[0009] An active slurry, the active slurry comprises an active material and an organic solvent, the solid content of the active slurry is 45wt%-60wt%;

[0010] The raw material of the active material comprises, by mass fraction:

[0011] Active substance, 93.5wt%-97.5wt%;

[0012] Binder, 1.5wt%-4.0wt%;

[0013] Conductive substance, 1.0wt%-2.5wt%.

[0014] Further, the active substance comprises one or more of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and activated carbon;

[0015] The binder comprises one or more of polyvinylidene fluoride, polyvinyl alcohol, and polytetrafluoroethylene;

[0016] The conductive substance comprises one or more of carbon black, graphene, carbon nanotubes, and conductive graphite;

[0017] The organic solvent is one or more of N-methylpyrrolidone, dimethylformamide, and dimethyl sulfoxide.

[0018] Further, the active substance comprises lithium nickel cobalt manganese oxide and activated carbon, and the mass ratio of the lithium nickel cobalt manganese oxide to the activated carbon is 1:10 to 10:1.

[0019] Further, the conductive substance comprises graphene and carbon black, and the mass ratio of the graphene to the carbon black is 0.2:1.0 to 1.0:1.0.

[0020] Alternatively, the conductive substance comprises carbon nanotubes and carbon black, and the mass ratio of the carbon nanotubes to the carbon black is 0.2:1.0 to 1.0:1.0.

[0021] In a second aspect, a method for preparing an active paste comprises the following technical scheme:

[0022] A method for preparing an active paste comprises the following process:

[0023] In a vacuum state, a binder is added to an organic solvent for first stirring, then a conductive substance is added for second stirring, and finally an active substance is added for third stirring. After preliminary mixing, high-speed stirring and low-speed stirring are sequentially performed, and the active paste is obtained.

[0024] Further, in the vacuum state, the vacuum degree is 10 -2 Pa to 10 -3 Pa.

[0025] Further, the first stirring comprises the following process: stirring at a speed of 80 rpm to 120 rpm for 4 min to 6 min, then stirring at a speed of 250 rpm to 350 rpm for 4 min to 6 min, and finally stirring at a speed of 500 rpm to 700 rpm for 250 min to 350 min.

[0026] The second stirring comprises the following process: stirring at a speed of 80 rpm to 120 rpm for 4 min to 6 min, then stirring at a speed of 250 rpm to 350 rpm for 4 min to 6 min, and finally stirring at a speed of 500 rpm to 700 rpm for 150 min to 200 min.

[0027] The third stirring includes the following process: stirring at 80 rpm-120 rpm for 4 min-6 min, then stirring at 250 rpm-350 rpm for 4 min-6 min, and finally stirring at 500 rpm-700 rpm for 800 min-900 min.

[0028] The high-speed stirring process: stirring at 1200 rpm-1300 rpm for 150 min-200 min.

[0029] The low-speed stirring process: stirring at 15 rpm-25 rpm for 45 min-65 min.

[0030] In a third aspect, a positive electrode tab adopts the following technical solution:

[0031] A positive electrode tab includes a current collector and an active coating layer formed by solidifying the active slurry on the surface of the current collector, the surface density of the active coating layer is 25 mg / cm 2 -50 mg / cm 2 , and the thickness of the active coating layer on one side is 100 μm-160 μm.

[0032] The current collector is coated with a graphene coating layer with a thickness of 1 μm-3 μm on both sides, and the current collector includes one of smooth or frosted perforated aluminum foil or non-perforated aluminum foil.

[0033] In a fourth aspect, a preparation method of a positive electrode tab adopts the following technical solution:

[0034] A preparation method of a positive electrode tab includes the following process: coating the active slurry on the surface of a current collector, the coating roller speed is 300 mm / min-350 mm / min, the roller speed ratio is 1.3-1.7, drying at a temperature of 120℃-150℃, and then rolling, the compaction degree is controlled to be 2.0-2.4 g / cm 3 , and the positive electrode tab is obtained.

[0035] In a fifth aspect, an application of a positive electrode tab adopts the following technical solution:

[0036] An application of the above-mentioned positive electrode tab in electric vehicles, power grid energy storage, industrial automation, and renewable energy systems.

[0037] The beneficial effects of the present application are as follows:

[0038] The active slurry provided by the application is used as the coating material of the positive electrode sheet, and the overall electrochemical performance and structural stability of the positive electrode sheet are improved by optimizing the proportion and solid content of the active material, the binder and the conductive material; the high proportion of the active material enhances the capacity performance of the coating layer, which helps to improve the energy density of the hybrid capacitor; the appropriate amount of the binder ensures that the coating layer has good adhesion and mechanical strength, reduces the risk of coating peeling during the cycle process, and prolongs the service life of the electrode sheet; at the same time, the reasonable proportion of the conductive material improves the electron conduction efficiency, reduces the internal resistance, and enhances the power characteristics of the electrode sheet; this active slurry formula not only enables the positive electrode coating to have excellent charge storage and transmission capacity, but also maintains the stability of the electrode sheet after multiple cycles, realizes the combination of high performance and long life, and provides reliable technical support for efficient energy storage applications. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 The charge-discharge curve of the 2032 type button cell composed of the positive electrode sheet of Example 1 at a current density of 0.5C is shown in the figure;

[0040] Figure 2 The charge-discharge test graph of the 2032 type button cell composed of the positive electrode sheet of Example 1 at different rates is shown in the figure;

[0041] Figure 3 The cycle performance test graph of the 2032 type button cell composed of the positive electrode sheet of Example 1 at a rate of 0.5C is shown in the figure. DETAILED DESCRIPTION

[0042] The active slurry, the positive electrode sheet and the preparation method thereof described in the application are further specifically described in combination with the examples. For the sake of simple description, all alternative technical features and embodiments contained in the application cannot be enumerated in this document, and therefore those skilled in the art should know that any technical feature and embodiment in the examples does not limit the protection scope of the application, and the protection scope of the application includes any alternative technical feature and embodiment taken by those skilled in the art without creative labor. Specifically, the embodiments obtained by replacing any technical feature in the application or combining any two or more technical features provided by the application should be within the protection scope of the application.

[0043] The active slurry provided in this embodiment includes an active material and an organic solvent, and the solid content of the active slurry is 45wt%-60wt%;

[0044] The raw material of the active material includes, by mass fraction:

[0045] Active material, 93.5wt%-97.5wt%;

[0046] binder, 1.5wt%-4.0wt%;

[0047] conductive substance, 1.0wt%-2.5wt%.

[0048] The active slurry provided in the embodiment is composed of active materials and organic solvents in a specific ratio, achieving excellent electrochemical performance and structural stability. The solid content is set at 45wt%-60wt%, ensuring the appropriate viscosity and uniform dispersion effect of the slurry, making the coating process more stable and efficient; in the active material, the high proportion of active substances endows the slurry with high energy storage capacity and energy density; the appropriate amount of binder enhances the adhesion and mechanical strength of the coating, preventing the peeling of the coating during the cycle process, and improving the durability of the pole piece. At the same time, the addition of conductive substance forms a good conductive network, effectively reducing the internal resistance and improving the current conduction performance.

[0049] This formula combination optimizes the overall performance of the active slurry, ensures the stability and high efficient conductivity of the positive pole piece in multiple charge-discharge cycles, and meets the application requirements of high energy density and long service life; the slurry provides a solid material foundation for realizing higher performance energy storage equipment.

[0050] In some embodiments, the active substance includes one or more of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and activated carbon;

[0051] The binder includes one or more of polyvinylidene fluoride, polyvinyl alcohol, and polytetrafluoroethylene;

[0052] The conductive substance includes one or more of carbon black, graphene, carbon tube, and conductive graphite;

[0053] The organic solvent is one or more of N-methyl pyrrolidone, dimethylformamide, and dimethyl sulfoxide.

[0054] The diversified selection of active substances, binders, conductive substances, and organic solvents ensures the high energy density, excellent conductivity, and long cycle life of the positive pole piece. By selecting lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, activated carbon, etc., the pole piece can achieve high capacity and voltage output, adapting to different energy storage needs. The application of various binders (such as polyvinylidene fluoride, polyvinyl alcohol, etc.) enhances the adhesion and flexibility of the coating and the substrate, avoiding possible peeling phenomena during the charge-discharge process, and improving the stability of the pole piece.

[0055] In terms of conductive substances, by adding materials such as carbon black, graphene, and carbon tubes, a high-efficiency conductive network is constructed, significantly improving electronic conduction efficiency, reducing resistance, and enhancing power density. In particular, the high conductivity of graphene and carbon tubes enables the electrode sheet to maintain excellent conductive performance at high rates. N-methyl pyrrolidone (NMP), dimethylformamide, and dimethyl sulfoxide as organic solvents have good solubility, making the mixing of the slurry more uniform and providing appropriate viscosity and fluidity to ensure the formation of a uniform coating during coating.

[0056] The flexibility of this material combination provides a wide range of choices for the application of positive electrode sheets, not only exhibiting superior energy and power density, but also having extremely high structural stability, meeting the needs of different energy storage devices for long cycle life and high energy output.

[0057] In some embodiments, the active material includes lithium nickel cobalt manganese oxide and activated carbon, and the mass ratio of lithium nickel cobalt manganese oxide to activated carbon is 1:10 to 10:1.

[0058] Using lithium nickel cobalt manganese oxide and activated carbon as the active material combination and setting the mass ratio in the range of 1:10 to 10:1 can achieve an ideal balance between energy density and power density. Lithium nickel cobalt manganese oxide (NCM) as a high-capacity battery active material has a high energy density, which can provide significant energy storage capacity for the positive electrode sheet; and activated carbon has a high specific surface area, which is beneficial for the rapid charge and discharge process, thereby improving the power density and charging and discharging speed.

[0059] By adjusting the ratio of lithium nickel cobalt manganese oxide and activated carbon, performance optimization can be achieved according to different application requirements. A higher ratio of lithium nickel cobalt manganese oxide is suitable for applications that require higher energy density, such as energy storage systems; while a higher ratio of activated carbon can enhance the power performance and cycle stability of the electrode, suitable for devices that require high power output. The flexibility of this combination not only expands the application field of the positive electrode sheet, but also ensures the best electrochemical performance under various conditions, improving the overall energy storage efficiency and durability of the hybrid capacitor.

[0060] In some embodiments, the conductive substance includes graphene and carbon black, and the mass ratio of graphene to carbon black is 0.2:1.0 to 1.0:1.0.

[0061] Alternatively, the conductive substance includes carbon tubes and carbon black, and the mass ratio of carbon tubes to carbon black is 0.2:1.0 to 1.0:1.0.

[0062] Graphene and carbon tubes can effectively improve the continuity of the electronic conduction path and the stability of the electrode material due to their high electrical conductivity and strong mechanical strength; carbon black, as a traditional conductive filler, has stable electrochemical properties, and after being compounded with graphene or carbon tubes, it can supplement the defects in the conductive network and enhance the overall electrical conductivity.

[0063] By adjusting the ratio of graphene or carbon tubes to carbon black, a balance between high electrical conductivity and cost control can be achieved; a higher proportion of graphene or carbon tubes helps to form an excellent conductive network, suitable for applications that require high power output; while a higher proportion of carbon black improves the stability and dispersibility of the slurry, suitable for scenarios with longer cycle life; such conductive materials not only reduce the internal resistance of the slurry, but also ensure the structural integrity during multiple charge and discharge cycles, thereby enhancing the power characteristics, energy density and long cycle stability of the positive electrode sheet.

[0064] The embodiment provides a preparation method of an active slurry, including the following processes:

[0065] In a vacuum state, the binder is added to the organic solvent for the first stirring, then the conductive substance is added for the second stirring, and finally the active substance is added for the third stirring. After preliminary mixing, high-speed stirring and low-speed stirring are performed in sequence, and the active slurry is obtained.

[0066] By adding the binder, the conductive substance and the active substance in sequence in a vacuum state and through step-by-step stirring treatment, the uniformity, stability and electrochemical performance of the slurry are significantly improved. First, the binder is added in a vacuum environment and stirred for the first time, which effectively prevents air bubbles from being entrained and ensures that the binder is fully dissolved and uniformly dispersed. Then, the conductive substance is added and stirred for the second time, gradually forming a conductive network and improving the electrical conductivity of the slurry. Finally, by adding the active substance and stirring for the third time, the active material is fully mixed with the conductive network and the binder, ensuring the electrochemical activity and uniform distribution of the material.

[0067] The subsequent high-speed stirring further improves the dispersibility and fluidity of the slurry, so that the components are closely combined; the low-speed stirring reduces air bubbles and unstable factors, improving the stability and coating effect of the slurry. The staged stirring of the whole process ensures the rheological properties of the slurry, greatly improving the density, durability and cycle life of the positive electrode sheet formed after coating, thereby realizing high energy density and high power output.

[0068] In some embodiments, in a vacuum state, the vacuum degree is 10 -2 Pa~10 -3 Pa.

[0069] The vacuum degree is set to The uniformity and overall quality of the slurry can be significantly improved; in this vacuum state, the air in the stirring process is effectively discharged, preventing the generation and entrainment of air bubbles, reducing the porosity of the slurry, and thus improving the density of the material; in addition, the stirring under vacuum allows the binder, conductive material and active material to fully contact and uniformly disperse in the slurry, avoiding the problems of particle agglomeration and uneven distribution; the vacuum condition not only improves the flowability and coating effect of the slurry, but also enhances the structural stability of the positive electrode sheet, effectively improving its electrochemical performance and durability in multiple charge-discharge cycles, so that the prepared positive electrode sheet has higher energy density and power characteristics, and is suitable for high-performance energy storage applications.

[0070] In some embodiments, the first stirring includes the following process: stirring at a speed of 80 rpm-120 rpm for 4-6 min, then stirring at a speed of 250 rpm-350 rpm for 4-6 min, and finally stirring at a speed of 500 rpm-700 rpm for 250-350 min;

[0071] The second stirring includes the following process: stirring at a speed of 80 rpm-120 rpm for 4-6 min, then stirring at a speed of 250 rpm-350 rpm for 4-6 min, and finally stirring at a speed of 500 rpm-700 rpm for 150-200 min;

[0072] The third stirring includes the following process: stirring at a speed of 80 rpm-120 rpm for 4-6 min, then stirring at a speed of 250 rpm-350 rpm for 4-6 min, and finally stirring at a speed of 500 rpm-700 rpm for 800-900 min;

[0073] High-speed stirring process: stirring at a speed of 1200 rpm-1300 rpm for 150-200 min;

[0074] Low-speed stirring process: stirring at a speed of 15 rpm-25 rpm for 45-65 min.

[0075] A detailed multi-stage stirring process is adopted to ensure the uniformity, stability and electrochemical performance of the active slurry. In the first stirring, the binder is gradually dispersed in the organic solvent at a low speed (80 rpm ~ 120 rpm) for 4 ~ 6 min to prevent the violent mixing of the binder and solvent from causing bubble formation and stratification. Then, the binder and solvent are further mixed at a medium speed (250 rpm ~ 350 rpm) to ensure the preliminary uniformity of the slurry. Finally, the binder and solvent are completely mixed at a high speed (500 rpm ~ 700 rpm) for a long time (250 ~ 350 min) to form a stable binder solution and lay a good foundation for the subsequent addition of conductive substances.

[0076] In the second stirring, the conductive substances are gradually added and the three-stage speed change is repeated to ensure the uniform distribution of the conductive substances in the slurry. The pre-mixing at low and medium speeds for a short time can reduce the local conductivity difference caused by uneven dispersion of the conductive substances, and then the conductive network is fully formed by stirring at a high speed (500 rpm ~ 700 rpm) for a long time (150 ~ 200 min). In this way, the conductive substances can be uniformly distributed in the slurry, reducing the loss of electrochemical performance caused by uneven resistance and ensuring the conductivity of the positive electrode sheet.

[0077] In the third stirring stage, the active substances are added and fully dispersed and homogenized by similar three-stage stirring. First, low speed (80 rpm ~ 120 rpm) and medium speed (250 rpm ~ 350 rpm) stirring for 4 ~ 6 min provides a gentle stirring environment for the preliminary dispersion of the active substances, avoiding uneven dispersion caused by adding materials at high speed. Then, stirring at a high speed (500 rpm ~ 700 rpm) for 800 ~ 900 min ensures the full integration of the active substances with the conductive substances and the binder, maximally reduces the agglomeration phenomenon, and makes the dispersion and uniformity of the slurry reach the best level.

[0078] Finally, all components in the slurry are thoroughly mixed by high-speed stirring (1200 rpm-1300 rpm, 150-200 min) to ensure the conductivity and fluidity of the material. Then, low-speed stirring (15 rpm-25 rpm, 45-65 min) is applied to release the tiny bubbles inside the slurry, reduce the porosity of the slurry, and make the slurry more stable. After this multi-stage and multi-rate stirring process, the prepared active slurry reaches an ideal state in terms of uniformity, conductivity, fluidity, and stability, providing effective support for the high energy density and long cycle life of the positive electrode sheet. This method realizes the perfect fusion of each component through fine stirring process control, thereby improving the electrochemical performance of the slurry and the service life of the electrode sheet, and making it exhibit excellent energy storage effect and stability in practical applications.

[0079] The positive electrode sheet provided in this embodiment includes a current collector and an active coating layer formed by solidifying the active slurry on the surface of the current collector, and the areal density of the active coating layer is 25 mg / cm 2 - 50 mg / cm 2 , and the single-sided active coating layer has a thickness of 100 μm-160 μm.

[0080] The current collector is coated with a graphene coating layer with a thickness of 1 μm-3 μm on both sides, and the current collector includes one of smooth or frosted perforated aluminum foil or non-perforated aluminum foil.

[0081] The positive electrode sheet provided in this embodiment includes a current collector and an active coating layer formed by solidifying the active slurry on the surface of the current collector, and the areal density of the active coating layer is 25 mg / cm 2 - 50 mg / cm 2 , and the single-sided active coating layer has a thickness of 100 μm-160 μm.

[0082] The current collector is coated with a graphene coating layer with a thickness of 1 μm-3 μm on both sides, and the current collector includes one of smooth or frosted perforated aluminum foil or non-perforated aluminum foil.

[0083] This embodiment provides a method for preparing a positive electrode sheet, comprising the following steps: coating an active slurry onto the surface of a current collector at a coating roller speed of 300 mm / min to 350 mm / min and a roller speed ratio of 1.3 to 1.7; drying at a temperature of 120℃ to 150℃; and then rolling to control the compaction degree to 2.0 to 2.4 g / cm³. 3 This yields the positive electrode sheet.

[0084] The positive electrode preparation method in this embodiment optimizes the coating, drying, and rolling processes to ensure the uniformity, structural stability, and excellent electrochemical performance of the electrode. First, the active slurry is uniformly coated onto the current collector surface at a coating roller speed of 300 mm / min to 350 mm / min, using a roller speed ratio of 1.3 to 1.7 to ensure consistent coating thickness and areal density. These process parameters control the spread of the slurry on the current collector surface, resulting in a more uniform distribution of the active material and avoiding performance fluctuations caused by uneven coating.

[0085] Subsequently The slurry is dried at a specific temperature to ensure complete evaporation of the solvent, thus forming a stable coating structure. This drying temperature effectively prevents the coating from cracking or peeling, while ensuring the density of the electrode surface.

[0086] Finally, the coating layer is further compacted using a rolling process, which allows the active material to be tightly bonded to the current collector, significantly reducing the internal resistance of the electrode and enhancing conductivity and structural stability. The positive electrode prepared by this method not only has high energy density and power density, but also good cycle stability and mechanical strength, making it suitable for high-performance energy storage applications.

[0087] The compaction degree of the positive electrode sheet is controlled between 2.0 and 2.4 g / cm³. 3 Within this range, the energy density and mechanical stability of the electrode are significantly improved; this compaction range ensures close contact between active material particles, forming a continuous conductive network, reducing internal porosity, thereby reducing electrode internal resistance and improving current conduction efficiency; at the same time, the appropriate compaction enhances the adhesion between the coating layer and the current collector, effectively reducing the risk of material peeling during charge-discharge cycles and extending the cycle life of the electrode.

[0088] Furthermore, controlling the compaction degree within this range allows for a balance between high power density and mechanical toughness. Too low a compaction degree may result in insufficient energy density, while too high a degree may affect the coating's conductivity and structural stability. Maintaining the compaction degree between 2.0 and 2.4 g / cm³ is effective. 3 The positive electrode in these embodiments has higher energy storage efficiency, long cycle performance and good mechanical strength, making it suitable for energy storage devices that require high energy density and high stability.

[0089] The application provides an application of the positive electrode tab in an electric vehicle, a power grid energy storage, industrial automation, and a renewable energy system.

[0090] The application of the positive electrode tab in an electric vehicle, a power grid energy storage, industrial automation, and a renewable energy system provided by the application fully plays the advantages of high energy density, high power density, and excellent cycle stability. In the field of electric vehicles, the positive electrode tab can support high-rate charging and discharging, meet the needs of fast charging, long endurance, and high power output of electric vehicles, enable the battery to realize fast energy replenishment in a short time, prolong the endurance mileage, and improve the driving experience. In addition, the high cycle life characteristics of the tab ensure that the electric vehicle battery maintains stable capacity output during long-term use, thereby prolonging the overall life of the battery, reducing the frequency of replacement, and reducing maintenance costs.

[0091] In the field of power grid energy storage, the battery prepared from the positive electrode tab can efficiently store and release energy, adapt to the load balancing and peak shaving needs of the power system. In areas with significant peak-valley power differences, the battery can store energy when power demand is low and release energy when power demand is high, providing sustained and stable power support for the power grid. This energy storage capability not only improves the stability and safety of the power grid operation, but also effectively utilizes the volatility of renewable energy generation, improving the grid-connected utilization rate of renewable energy.

[0092] In the field of industrial automation, the high-performance battery prepared from the positive electrode tab can provide reliable energy support for industrial equipment, especially in scenarios requiring fast charging and discharging and high power output, such as robots and numerical control machine tools in automated production lines. Its high power density enables the equipment to run efficiently and continuously under high load, avoiding production interruptions caused by power shortages and improving the automation level and production efficiency of the production line.

[0093] In addition, in the renewable energy system, the application of the positive electrode tab can help balance the volatility of renewable energy sources such as solar and wind energy. Due to the instability of renewable energy generation, the addition of an efficient energy storage system can store energy when light or wind is strong and release energy when demand increases or power supply is insufficient, thereby ensuring the stability of energy supply. Its long cycle life and high efficiency enable the energy storage equipment to run stably for a long time, providing reliable energy buffering for the renewable energy system, promoting the efficient use of renewable energy, and promoting the popularization of clean energy.

[0094] In summary, the positive electrode tab in the application has a wide application prospect in electric vehicles, power grid energy storage, industrial automation, and renewable energy systems due to its excellent electrochemical performance. Through improving energy utilization efficiency, reducing costs, and prolonging equipment life, the application promotes technological progress and sustainable development in multiple fields.

[0095] Embodiment

[0096] Embodiment 1

[0097] Embodiment 1 provides an active slurry, the active slurry comprising an active material and an organic solvent, the solid content being 45wt%; wherein the organic solvent is N-methyl pyrrolidone;

[0098] The raw material of the active material comprises, in mass fraction:

[0099] The active material, 93.5wt%; the binder, 4.0wt%; the conductive material, 2.5wt%;

[0100] The active material comprises lithium nickel cobalt manganese oxide and activated carbon, the mass ratio of lithium nickel cobalt manganese oxide to the activated carbon being 1:10; the binder is polyvinylidene fluoride; the conductive material comprises graphene and carbon black, the mass ratio of graphene to carbon black being 1.0:1.0.

[0101] Embodiment 1 provides a preparation method of an active slurry, comprising the following steps:

[0102] Under the condition that the vacuum degree is 10 -2 Pa, the binder is added to the organic solvent, stirred at the speed of 100rpm for 5min, then the speed is increased to 300rpm for 5min, and finally stirred at 600rpm for 300min to obtain a uniform binder solution.

[0103] The conductive material is added to the binder solution, and the stirring is continued at 100rpm for 5min, then at 300rpm for 5min, and finally at 600rpm for 180min to ensure uniform dispersion of the conductive agent, to obtain a conductive binder solution.

[0104] The active material is added to the conductive binder solution, mixed, then stirred at 100rpm for 5min, increased to 300rpm for 5min, and finally stirred at 600rpm for 840min; then the stirring speed is increased to 1200rpm, high-speed stirring is performed for 180min, and finally low-speed stirring is performed at the speed of 20rpm for 50min, to complete the mixing of the slurry, to obtain an active slurry.

[0105] Embodiment 1 also provides a positive electrode sheet, comprising a current collector and an active coating layer formed by solidifying the active slurry on the surface of the current collector; the active coating layer has an areal density of 35mg / cm 2 , and a single-sided active coating layer thickness of 130μm.

[0106] The current collector is a smooth surface hole aluminum foil with a thickness of 12μm, and is coated with a graphene coating layer of 1μm on both sides.

[0107] The embodiment 1 also provides a preparation method of the positive electrode tab, comprising the following steps:

[0108] The active slurry is uniformly coated on both sides of the aluminum foil current collector, the speed of the coating roller is adjusted to 330 mm / min, and the roller speed ratio is set to 1.5; then, drying is performed at a drying temperature of 140 DEG C to ensure rapid evaporation of the solvent; then, by adjusting the parameters of the coating machine, the double-sided coating area density of the positive electrode tab is controlled to be 35 mg / cm 2 , and the single-sided active coating thickness is 130 pm; finally, a rolling process is performed, the compaction degree is controlled to be 2.2 g / cm 3 by using a multiple rolling method, so that the tab has good uniformity and density consistency, and the positive electrode tab is obtained.

[0109] The embodiment 2

[0110] The embodiment 2 provides an active slurry, the active slurry comprising an active material and an organic solvent, and the solid content is 50 wt%; wherein the organic solvent is dimethylformamide;

[0111] The raw material of the active material comprises, by mass fraction:

[0112] active substance, 95 wt%; binder, 3.0 wt%; conductive substance, 2.0 wt%;

[0113] The active substance comprises lithium nickel cobalt manganese oxide and activated carbon, and the mass ratio of the lithium nickel cobalt manganese oxide to the activated carbon is 5:5; the binder is polytetrafluoroethylene; and the conductive substance comprises graphene and carbon black, and the mass ratio of the graphene to the carbon black is 0.2:1.0.

[0114] The embodiment 2 provides a preparation method of the active slurry, comprising the following steps:

[0115] The binder is added to the organic solvent under the condition that the vacuum degree is 10 -2 Pa, stirring is performed at a rotating speed of 80 rpm for 6 min, the rotating speed is increased to 250 rpm for stirring for 6 min, and finally stirring is performed at 500 rpm for 350 min to obtain a uniform binder solution.

[0116] The conductive substance is added to the binder solution, stirring is continuously performed at 80 rpm for 6 min, then stirring is performed at 250 rpm for 6 min, and finally stirring is performed at 500 rpm for 200 min to ensure uniform dispersion of the conductive agent, and a conductive binder solution is obtained.

[0117] The active material is added to the conductive adhesive solution, mixed, and then stirred at 80 rpm for 6 min, increased to 250 rpm for 6 min, and finally stirred at 500 rpm for 900 min; then, the stirring speed is increased to 1200 rpm, stirred at high speed for 200 min, and finally stirred at low speed at 15 rpm for 55 min to complete the mixing of the slurry and obtain the active slurry.

[0118] Example 2 also provides a positive electrode tab, including a current collector and an active coating layer formed by curing the active slurry on the surface of the current collector; the active coating layer has an areal density of 25 mg / cm 2 , and a single-sided active coating layer thickness of 100 μm.

[0119] The current collector is a smooth-surfaced, perforated aluminum foil with a thickness of 12 μm, and is coated with a graphene coating on both sides with a thickness of 3 μm.

[0120] Example 2 also provides a method for preparing a positive electrode tab, including the following steps:

[0121] The active slurry is uniformly coated on both sides of the aluminum foil current collector, the speed of the coating roller is adjusted to 320 mm / min, and the roller speed ratio is set to 1.7; then, drying is performed at a drying temperature of 150°C to ensure rapid evaporation of the solvent; then, by adjusting the parameters of the coating machine, the double-sided coating areal density of the positive electrode tab is controlled to be 25 mg / cm 2 , and the single-sided active coating layer thickness is controlled to be 100 μm; finally, a rolling process is performed, a multiple rolling method is used to control the compaction degree to be 2.2 g / cm 3 , to ensure that the tab has good uniformity and density consistency, and the positive electrode tab is obtained.

[0122] Example 3

[0123] Example 3 provides an active slurry, the active slurry including an active material and an organic solvent, and having a solid content of 55 wt%; the organic solvent is N-methyl pyrrolidone;

[0124] The raw materials of the active material include, by mass fraction:

[0125] The active material is 97.5 wt%, the binder is 1.5 wt%, and the conductive material is 1.0 wt%;

[0126] The active material includes lithium nickel cobalt manganese oxide and activated carbon, and the mass ratio of lithium nickel cobalt manganese oxide to activated carbon is 10:1; the binder is polyvinyl alcohol; and the conductive material includes carbon tubes and carbon black, and the mass ratio of carbon tubes to carbon black is 0.2:1.0.

[0127] Example 3 provides a method for preparing an active slurry, including the following steps:

[0128] The binder was added into the organic solvent under the condition of 10 Pa vacuum degree, stirred at 120 rpm for 4 min, then the stirring speed was increased to 350 rpm for 4 min, and finally stirred at 700 rpm for 250 min to obtain a uniform binder solution. -2 The binder was added into the organic solvent under the condition of 10 Pa vacuum degree, stirred at 120 rpm for 4 min, then the stirring speed was increased to 350 rpm for 4 min, and finally stirred at 700 rpm for 250 min to obtain a uniform binder solution.

[0129] The conductive material was added into the binder solution, and the stirring was continued at 120 rpm for 4 min, then at 350 rpm for 4 min, and finally at 700 rpm for 150 min to ensure uniform dispersion of the conductive agent, to obtain a conductive binder solution.

[0130] The active material was added into the conductive binder solution, mixed, and then stirred at 120 rpm for 4 min, increased to 350 rpm for 4 min, and finally stirred at 700 rpm for 800 min; then the stirring speed was increased to 1300 rpm, high-speed stirring was performed for 150 min, and finally low-speed stirring was performed at 25 rpm for 45 min to complete the mixing of the slurry, to obtain an active slurry.

[0131] Example 3 also provides a positive electrode tab, comprising a current collector and an active coating layer formed by curing the active slurry on the surface of the current collector; the active coating layer has an areal density of 50 mg / cm 2 , and a single-sided active coating layer thickness of 160 μm.

[0132] The current collector is a smooth-surfaced hole-bearing aluminum foil with a thickness of 15 μm, and is coated with a graphene coating layer on both sides with a thickness of 2 μm.

[0133] Example 3 also provides a method for preparing a positive electrode tab, comprising the following steps:

[0134] The active slurry was uniformly coated on both sides of the aluminum foil current collector, the speed of the coating roller was adjusted to 350 mm / min, and the roller speed ratio was set to 1.3; then, drying was performed at a drying temperature of 120°C to ensure rapid evaporation of the solvent; then, by adjusting the parameters of the coating machine, the double-sided coating areal density of the positive electrode tab was controlled to be 50 mg / cm 2 , and the single-sided active coating layer thickness was controlled to be 160 μm; finally, a rolling process was performed, a multiple-rolling method was used, and the compaction degree was controlled to be 2.4 g / cm 3 , to ensure that the tab has good uniformity and density consistency, to obtain a positive electrode tab.

[0135] Example 4

[0136] The active slurry provided in Example 4 is different from that of Example 3 in that the conductive material of Example 4 comprises carbon tubes and carbon black, and the mass ratio of the carbon tubes to the carbon black is 1:1.

[0137] The preparation method of the active slurry, the positive electrode sheet, and the preparation method of the positive electrode sheet provided in Example 4 are the same as those of Example 3.

[0138] Comparative Example 1

[0139] Comparative Example 1 provides an active slurry which is different from Example 1 in that the solid content of the active slurry is 40 wt%.

[0140] The preparation method of the active slurry, the positive electrode sheet, and the preparation method of the positive electrode sheet provided in Comparative Example 1 are the same as those of Example 1.

[0141] The preparation method of the active slurry, the positive electrode sheet, and the preparation method of the positive electrode sheet provided in Comparative Example 1 are the same as those of Example 1.

[0142] Comparative Example 2

[0143] Comparative Example 2 provides an active slurry which is different from Example 1 in that the solid content of the active slurry is 65 wt%.

[0144] The preparation method of the active slurry, the positive electrode sheet, and the preparation method of the positive electrode sheet provided in Comparative Example 2 are the same as those of Example 1.

[0145] Comparative Example 3

[0146] Comparative Example 3 provides an active slurry which is the same as Example 1.

[0147] The preparation method of the active slurry provided in Comparative Example 3 is different from Example 1 in that the preparation method of the active slurry provided in Comparative Example 1 does not perform gradient stirring, and specifically as follows:

[0148] The preparation method of the active slurry provided in Comparative Example 3 includes the following steps:

[0149] Under the condition that the vacuum degree is 10 -2 Pa, the binder is added to the organic solvent, and stirred at 600 rpm for 300 min to obtain a uniform binder solution;

[0150] The conductive substance is added to the binder solution, and stirred at 600 rpm for 180 min to obtain a conductive binder solution;

[0151] The active substance is added to the conductive binder solution, and stirred at 600 rpm for 840 min; then, the stirring speed is increased to 1200 rpm, and stirred at high speed for 180 min; finally, low-speed stirring is performed at 20 rpm for 50 min to complete the mixing of the slurry, and obtain the active slurry.

[0152] The positive electrode sheet and the preparation method of the positive electrode sheet provided in Comparative Example 3 are the same as those of Example 1.

[0153] Comparative Example 4

[0154] The active slurry provided by Comparative Example 4 is the same as that of Example 1.

[0155] The method for preparing the active slurry provided by Comparative Example 4 is different from that of Example 1 in that the active slurry provided by Comparative Example 2 is not stirred under vacuum.

[0156] The positive electrode sheet provided by Comparative Example 4 and the method for preparing the positive electrode sheet are the same as those of Example 1.

[0157] Comparative Example 5

[0158] The active slurry provided by Comparative Example 5 is the same as that of Example 1.

[0159] The method for preparing the active slurry provided by Comparative Example 5 is different from that of Example 1 in that no high-speed stirring and low-speed stirring are performed, and the details are as follows:

[0160] The method for preparing the active slurry provided by Comparative Example 5 includes the following steps:

[0161] The binder is added to the organic solvent under the condition that the vacuum degree is 10 -2 Pa, stirred at 100 rpm for 5 min, the stirring speed is increased to 300 rpm for 5 min, and finally stirred at 600 rpm for 300 min to obtain a uniform binder solution.

[0162] The conductive material is added to the binder solution, and the stirring is continued at 100 rpm for 5 min, then at 300 rpm for 5 min, and finally at 600 rpm for 180 min to ensure uniform dispersion of the conductive agent, to obtain a conductive binder solution.

[0163] The active material is added to the conductive binder solution, mixed, and then stirred at 100 rpm for 5 min, increased to 300 rpm for 5 min, and finally stirred at 600 rpm for 840 min; the mixing of the slurry is completed, and an active slurry is obtained.

[0164] The positive electrode sheet provided by Comparative Example 5 and the method for preparing the positive electrode sheet are the same as those of Example 1.

[0165] Comparative Example 6

[0166] The active slurry and the method for preparing the active slurry provided by Comparative Example 6 are the same as those of Example 1.

[0167] The positive electrode sheet provided by Comparative Example 6 is different from that of Example 1 in that the active coating area density is 20 mg / cm 2 .

[0168] Comparative Example 6 provides a method for preparing a positive electrode plate, which is different from Example 1 in that the double-sided coating surface density of the positive electrode plate is controlled to be 20 mg / cm by adjusting the parameters of the coating machine. 2 .

[0169] Comparative Example 7

[0170] Comparative Example 7 provides an active slurry, a method for preparing an active slurry, which is the same as Example 1.

[0171] Comparative Example 7 provides a positive electrode plate, which is different from Example 1 in that the active coating surface density is 55 mg / cm 2 .

[0172] Comparative Example 7 provides a method for preparing a positive electrode plate, which is different from Example 1 in that the double-sided coating surface density of the positive electrode plate is controlled to be 55 mg / cm by adjusting the parameters of the coating machine. 2 .

[0173] Comparative Example 8

[0174] Comparative Example 8 provides an active slurry, a method for preparing an active slurry, which is the same as Example 1.

[0175] Comparative Example 8 provides a positive electrode plate, which is different from Example 1 in that the single-sided active coating layer thickness is 90 μm.

[0176] Comparative Example 8 provides a positive electrode plate, which is different from Example 1 in that the single-sided active coating layer thickness is 90 μm by adjusting the parameters of the coating machine.

[0177] Comparative Example 9

[0178] Comparative Example 9 provides an active slurry, a method for preparing an active slurry, which is the same as Example 1.

[0179] Comparative Example 9 provides a positive electrode plate, which is different from Example 1 in that the surface of the current collector is not coated with graphene.

[0180] Comparative Example 9 provides a method for preparing a positive electrode plate, which is the same as Example 1.

[0181] Application Example

[0182] The positive electrode plates provided by Examples 1-4 and Comparative Examples 1-9 are respectively assembled into 2032 type button cells, which are assembled in a glove box in an argon environment, and the concentrations of humidity (water) and oxygen are both less than 1 ppm. The positive electrode plate provided by Example 1 is cut into a circular electrode with a diameter of 12 mm, a PP separator (Celgard 2500) is used, a pure lithium foil is used as a counter electrode, and LiPF6 (1.0 M, ethylene carbonate, dimethyl carbonate, volume ratio 1:1) is used as an electrolyte.

[0183] Performance Test

[0184] Electrode Tab Surface Active Coating Adhesion Test

[0185] A "Crosshatch Test" was performed on the positive electrode tabs provided in Examples 1-4 and Comparative Examples 1-9 to evaluate the adhesion between the active coating and the current collector.

[0186] 1. Purpose of Test

[0187] The Crosshatch Test is used to determine the strength of adhesion between the active coating and the current collector on a positive electrode tab. By scribing a specific grid pattern on the coating and combining with tape peeling, the adhesion level of the coating can be visually evaluated.

[0188] 2. Test Equipment

[0189] Crosshatch Knife: A multi-blade crosshatch knife is commonly used, with a spacing of 1 mm or 2 mm, and the appropriate spacing is chosen according to the thickness of the coating. The blade edge of the crosshatch knife is sharp and uniform in spacing to ensure the scribing effect.

[0190] Transparent Tape: A transparent tape with moderate adhesion (such as 3M's 600 series tape) is generally chosen to ensure that excessive damage to the coating does not occur during peeling.

[0191] Magnifying Glass or Microscope: Used to observe the state of the coating after scribing, with a magnification of 10x to 20x.

[0192] Ruler and Scale: Used to measure the depth and spacing of the scribe marks.

[0193] 3. Test Procedure

[0194] Sample Preparation: Ensure that the positive electrode tab sample is dry and clean, and fix it on a flat surface to prevent movement during testing.

[0195] Scribing Operation: Use the crosshatch knife to scribe parallel lines perpendicular to each other on the coating surface to form a grid pattern. A square grid with a spacing of 1 mm or 2 mm (such as 6x6 or 10x10) is recommended. When scribing, ensure that the blade cuts through the coating to the substrate surface, but does not damage the current collector.

[0196] Taping: Apply transparent tape to the scribed grid area and press the tape to ensure complete contact with the coating surface.

[0197] Peeling Operation: Quickly peel off the tape at an angle of about 45° and observe the peeling of the coating within the grid.

[0198] Result Observation: Observe the scribed area through a magnifying glass or microscope to evaluate the peeling of the coating.

[0199] 4. Result evaluation

[0200] The adhesion is evaluated by the degree of peeling of the coating. The adhesion rating of a general cross-hatch test is divided into 0-5 levels, with the specific standards as follows:

[0201] 0 level: no peeling or very little peeling, the coating is complete, indicating excellent adhesion.

[0202] 1 level: there is a small amount of peeling at the cut of the grid, but the peeling area is less than 5%, and the adhesion of the coating layer is very good.

[0203] 2 level: the peeling area is between 5% and 15%, and the adhesion is good.

[0204] 3 level: the peeling area is between 15% and 35%, indicating that the adhesion is general.

[0205] 4 level: the peeling area is between 35% and 65%, indicating that the adhesion is poor.

[0206] 5 level: most of the coating peels off, with a peeling area of more than 65%, indicating that the adhesion is very poor.

[0207] Generally, adhesion levels 0-2 are considered to meet the requirements, and levels 3 and below may need to improve the process or adjust the formula.

[0208] 5. Test conditions and precautions

[0209] Cross-hatch spacing selection: select appropriate spacing and blade depth according to the thickness of the coating to avoid damage to the current collector.

[0210] Adhesive tape selection: adhesive tapes with too high or too low adhesion will affect the test results, and transparent adhesive tapes with moderate adhesion are usually selected.

[0211] Peeling speed: maintain a 45° angle and peel quickly to ensure the stability and repeatability of the test.

[0212] Environmental conditions: test at room temperature and dry conditions to avoid the influence of high temperature or humidity on adhesion.

[0213] According to the above "cross-hatch test", the positive electrode plates provided by Examples 1-4 and Comparative Examples 1-9 were tested, and the test results are shown in Table 1 below.

[0214] Table 1 Adhesion rating of surfactant coating layer on positive electrode plate surface of Examples 1-4 and Comparative Examples 1-9

[0215]

[0216] LAND battery test

[0217] Specific capacity test: The specific capacity results of the example and comparative example samples are included to show the capacity difference of different positive electrode sheets under the same conditions.

[0218] Rate capability test: The charge and discharge capacity changes at different rates (e.g. 0.5C, 1C, 2C, 5C and 10C) are analyzed. The positive electrode sheets of the examples are expected to maintain higher capacity at high rates, while the comparative examples may exhibit greater capacity decline.

[0219] Cycle stability test: The positive electrode sheets are subjected to a cycle test of up to 2000 times, and the changes in specific capacity and charge-discharge efficiency are recorded to evaluate their cycle life. The examples show excellent stability, while the capacity retention rate of some comparative examples is relatively low.

[0220] Electrochemical impedance spectroscopy (EIS): used to measure the interface impedance and charge transfer impedance, further verifying the conductivity of the positive electrode sheet, the impedance of the examples is generally lower, suitable for high-power applications.

[0221] The capacity test, rate capability test and cycle stability test of the 2032 button cell battery composed of the positive electrode sheet provided in Example 1 are shown in the following table: Figures 1-3 The specific analysis is as follows:

[0222] 1. Specific capacity test

[0223] From the above table, it can be seen that: Figure 1 Figure 1 The charging and discharging curves of the positive electrode material in different voltage ranges are shown, with specific capacity (mAh / g) on the horizontal axis and voltage (V) on the vertical axis. As can be seen from the figure, there is a certain difference between the voltage curves of the charging and discharging processes, indicating that there is voltage polarization in the charging and discharging process of the material. This polarization may be due to internal resistance and interface impedance during the electrochemical reaction process, affecting the electrochemical performance of the material. The charging curve remains relatively flat on the high voltage platform, indicating that the lithium ion insertion of the electrode material is relatively uniform in this voltage range, and there is no significant phase change or material structure damage. This stable voltage platform is particularly important in battery applications, as it can provide stable energy output, thereby achieving higher energy density.

[0224] In the discharging process, the voltage platform is relatively flat and shows a relatively symmetrical shape compared to the charging process, indicating that the material has good reversibility and stability in the discharging process. This symmetry indicates that the material maintains good structural integrity during the charging and discharging cycle, especially without serious structural expansion or pulverization during the transition from charging to discharging. The stability of the discharging platform is directly related to the energy output efficiency of the battery, and a relatively flat discharging curve indicates that the material can provide sustained and stable energy output, which helps to improve the stability and consistency of the entire battery system.​

[0225] In addition, the difference between the charge curve and the discharge curve, i.e., the "voltage hysteresis" phenomenon, can be used to measure the electrochemical impedance of the electrode material. A smaller voltage hysteresis indicates a lower internal resistance and electrochemical impedance of the material, which is beneficial to improving the rate performance and energy efficiency. Lower voltage polarization also helps to reduce energy loss during charging and discharging, thereby improving the overall efficiency of the battery. Overall, the smooth and symmetric charge and discharge curves of the material demonstrate its good electrochemical reversibility and low internal resistance, and it can provide stable capacity output within a wide voltage range, verifying its suitability as a high-performance positive electrode material.

[0226] 2. Rate performance test

[0227] From the above results, it can be seen that the battery exhibits good rate performance. The charge and discharge curves of the battery at different rates are shown in the figure. It can be seen that the battery has a stable capacity output within a wide voltage range, and the charge and discharge curves are smooth and symmetric, indicating that the material has good electrochemical reversibility and low internal resistance. Figure 2 As can be seen from the above results, the battery exhibits good rate performance. The charge and discharge curves of the battery at different rates are shown in the figure. It can be seen that the battery has a stable capacity output within a wide voltage range, and the charge and discharge curves are smooth and symmetric, indicating that the material has good electrochemical reversibility and low internal resistance. Figure 2 The figure shows the specific capacity of the battery under different rate conditions, including 0.5C, 1C, 2C, 5C, and 10C rate test results. It can be seen that as the rate increases, the specific capacity decreases slightly, which is due to the limitation of ion diffusion rate and electron conduction rate of the electrode material at high rates, resulting in some active materials not fully participating in the reaction. Therefore, the decrease in capacity at high rates is a normal phenomenon, but it is observed that the material still maintains a relatively high specific capacity at 10C, which reflects the excellent rate performance of the positive electrode material.

[0228] The results of the rate performance test show that at 0.5C and 1C, the specific capacity of the battery is close to the theoretical capacity, indicating that the material can fully release its energy storage capacity at low rates. As the rate increases to 2C and 5C, the capacity decreases slightly but still remains at a high level, indicating that the material still has good fast charging and discharging performance at high rates, and can provide stable energy output in a short time. At the highest 10C rate, although the specific capacity decreases, it still shows relatively high energy storage capacity, which is ideal for high power requirements in practical applications.

[0229] In addition, the figure shows that the charge and discharge specific capacities are basically the same, indicating that the battery has a high coulomb efficiency at each rate. The stability of the coulomb efficiency indicates that the battery has a high energy conversion efficiency during charging and discharging at different rates, and the electrochemical reaction has good reversibility without significant side reactions or irreversible material loss. This high-efficiency electrochemical reaction also indicates that the material has strong structural stability and low resistance, allowing it to maintain high battery performance under different power output conditions. In summary, the rate performance test shows that the material can maintain high capacity and efficiency in a wide range from low to high rates, making it suitable for application in high-power energy storage systems.

[0230] 3. Cycle stability

[0231] It can be seen that Figure 3 It can be seen that Figure 3 The capacity retention and charge-discharge efficiency of the battery during long-term cycling are shown. It can be observed that after 2000 charge-discharge cycles, the specific charge capacity and specific discharge capacity of the battery do not show significant decay, and the charge-discharge efficiency remains at a high level. This excellent cycling stability indicates that the positive electrode material has excellent structural stability during long-term and high-frequency charge-discharge processes. The ability to maintain a high capacity retention rate during long-term cycling indicates that the material has strong electrochemical reaction reversibility and still provides sufficient active sites after multiple cycles.

[0232] During the cycling process, the specific discharge capacity of the battery remains at a relatively stable level, indicating that the material does not undergo significant structural changes or active loss during charge-discharge processes. This characteristic of the material is crucial for extending the battery life, as in practical applications, batteries often need to undergo thousands of charge-discharge cycles. The ability to maintain high capacity for such a long time indicates that the material has good structural durability during lithium intercalation and deintercalation, without serious problems such as crystal structure collapse, particle pulverization, or electrolyte decomposition, which is of great significance for the development of high-performance batteries.

[0233] In addition, the charge-discharge efficiency is always close to 100%, indicating that the material has extremely high coulombic efficiency during cycling. High coulombic efficiency means that the battery has almost no irreversible capacity loss during each cycle, indicating that the material has excellent chemical and mechanical stability and fewer side reactions. Through this cycling stability test, it can be seen that the positive electrode material not only has the ability to maintain high capacity for a long time, but also maintains its structure during multiple cycles, making it suitable for application in energy storage systems that require long life and high stability, such as electric vehicles and large-scale energy storage power stations. Overall, the results of the cycling stability test verify the high durability and high efficiency of the positive electrode material, providing strong support for its reliability in practical applications.

[0234] The positive electrode sheets provided by Examples 2-4 and Comparative Examples 1-9 were assembled into 2032 type button cells under the same conditions, and the capacity test, rate performance test and cycling stability test were carried out under the same conditions using the above test methods. The test results are shown in Table 2.

[0235] Table 2 Test results of 2032 type button cells assembled by positive electrode sheets of Examples 1-4 and Comparative Examples 1-9

[0236]

[0237] As shown in Table 2, there are significant differences in the electrochemical performance indicators such as initial specific capacity, rate capability, cycle stability, and charge transfer impedance between Examples 1-4 and Comparative Examples 1-9. These differences can be attributed to the optimization of different positive electrode sheet material formulations and preparation processes.

[0238] Initial specific capacity

[0239] The initial specific capacity of Example 1 reaches 220 mAh / g, slightly higher than other Examples 2-4, indicating that good results have been achieved in the optimization of the ratio of active material and conductive agent. In comparison, the initial specific capacity of the comparative examples is generally low, with the highest comparative example 1 only reaching 200 mAh / g, which indicates that the positive electrode material of the comparative examples has poor capacity performance in the initial state and cannot provide high storage capacity.

[0240] Rate capability

[0241] Examples 1-4 exhibit good capacity retention at different rates (0.5C to 10C). For example, at a rate of 10C, the specific capacity of Example 1 still reaches 180 mAh / g, which is significantly higher than that of the samples of the comparative examples. The capacity of the comparative examples decreases more significantly as the rate increases, especially at high rates (such as 5C and 10C), the specific capacity decreases significantly. The excellent rate performance of the examples shows that they have good conductivity and ion diffusion capacity, which enables them to maintain high specific capacity at high rates.

[0242] Cycle stability

[0243] The capacity retention rate of Example 1 after 2000 cycles reaches 95%, showing excellent cycle life, while other examples (2-4) also maintain a capacity retention rate of about 92-94%. In contrast, the capacity retention rate of the comparative example samples is generally low, with the highest comparative example 1 only maintaining 80% of the capacity, and other comparative example samples even decreasing to about 65%. This indicates that the materials in the examples have strong structural stability during the cycle process, and can better resist structural changes and electrochemical damage caused by repeated charging and discharging.

[0244] Charge transfer impedance

[0245] The charge transfer impedance of the examples is generally low, such as the internal resistance of Example 1 is 2.5 mΩ, while the charge transfer impedance of the comparative examples is relatively high, usually above 4.5 mΩ, and the highest comparative example 9 reaches 15.2 mΩ. Low internal resistance means low electrochemical polarization and higher electron conduction efficiency, so the low impedance of the examples indicates that their conductive network is more perfect, suitable for high-rate discharge applications. The high impedance of the comparative examples may lead to poor rate performance, which cannot meet the needs of high-power applications.

[0246] In summary, the positive electrode tabs of Examples 1-4 are superior to the comparative sample in terms of initial specific capacity, rate capability, cycle stability, and charge transfer impedance. This indicates that the positive electrode materials in the examples, through optimization of formulation and process, achieve higher electrochemical performance indicators, and can adapt to high energy density and high power density energy storage applications; the examples perform particularly well in high rate and long cycle, showing strong fast charging and discharging capacity and long life characteristics. This is crucial for applications in electric vehicles, grid energy storage, and industrial automation, etc., and can maintain stable performance in high power and high frequency use environments; the low impedance of the examples further proves their excellent electrical conductivity and ion conduction capacity, suitable for high rate discharge requirements. The high impedance of the comparative sample limits its rate performance and results in greater energy loss.

[0247] Overall, the positive electrode tabs of Examples 1-4 exhibit excellent electrochemical performance, suitable for use in high-end energy storage devices that require high energy density, excellent rate capability, and long cycle life, while the comparative sample has poor applicability due to performance limitations. These data provide experimental support for the material advantages of the present application and lay the foundation for its promotion in practical applications.

[0248] Other different forms of changes or variations can be made on the basis of the above description for those of ordinary skill in the art. Here, it is not necessary or possible to exhaust all embodiments, and the obvious changes or variations derived therefrom are still within the protection scope of the inventive claims.

Claims

1. A positive electrode plate, characterized in that, The invention includes a current collector and an active coating layer cured on the surface of the current collector. The active coating layer is made of an active slurry, which includes an active material and an organic solvent. The solid content of the active slurry is 45 wt% to 60 wt%. The active material, by mass fraction, includes: an active substance, 93.5 wt% to 97.5 wt%; a binder, 1.5 wt% to 4.0 wt%; and a conductive substance, 1.0 wt% to 2.5 wt%. The active material comprises lithium nickel cobalt manganese oxide and activated carbon, wherein the mass ratio of lithium nickel cobalt manganese oxide to activated carbon is 1:10 to 10:1; the conductive material comprises graphene and carbon black, wherein the mass ratio of graphene to carbon black is 0.2:1.0 to 1.0:1.0; or, the conductive material comprises carbon nanotubes and carbon black, wherein the mass ratio of carbon nanotubes to carbon black is 0.2:1.0 to 1.0:1.0; and the current collector is coated with a 1μm to 3μm graphene coating on both sides; the areal density of the active coating layer is 25 mg / cm³. 2 ~50 mg / cm 2 The thickness of the active coating layer on one side is 100μm~160μm; The method for preparing the active slurry includes the following steps: Under vacuum, the binder is added to the organic solvent for the first stirring, then the conductive material is added for the second stirring, and finally the active material is added for the third stirring. After initial mixing, high-speed stirring and low-speed stirring are performed in sequence to obtain the active slurry. The first stirring process includes the following steps: stirring at 80 rpm to 120 rpm for 4 to 6 minutes, then stirring at 250 rpm to 350 rpm for 4 to 6 minutes, and finally stirring at 500 rpm to 700 rpm for 250 to 350 minutes; the second stirring process includes the following steps: stirring at 80 rpm to 120 rpm for 4 to 6 minutes, then stirring at 250 rpm to 350 rpm for 4 to 6 minutes, and finally stirring at 500 rpm to 700 rpm for 150 to 200 minutes; the third stirring process includes the following steps: stirring at 80 rpm to 120 rpm for 4 to 6 minutes, then stirring at 250 rpm to 350 rpm for 4 to 6 minutes, and finally stirring at 500 rpm to 700 rpm for 800 to 900 minutes; the high-speed stirring process involves stirring at 1200 rpm. Stir at ~1300rpm for 150min~200min; the low-speed stirring process: stir at 15rpm~25rpm for 45min~65min.

2. The positive electrode sheet according to claim 1, characterized in that, The adhesive includes one or more of polyvinylidene fluoride, polyvinyl alcohol, and polytetrafluoroethylene; The organic solvent is one or more of N-methylpyrrolidone, dimethylformamide, and dimethyl sulfoxide.

3. The positive electrode sheet according to claim 1, characterized in that, The current collector includes either a smooth or frosted perforated aluminum foil or a non-perforated aluminum foil.

4. A method for preparing a positive electrode sheet as described in any one of claims 1 to 3, characterized in that, The process includes the following steps: coating the active slurry onto the surface of the current collector using a coating roller at a speed of 300 mm / min to 350 mm / min and a roller speed ratio of 1.3 to 1.7; drying at a temperature of 120℃ to 150℃; and then rolling to control the compaction degree to 2.0 to 2.4 g / cm³. 3 Thus, the positive electrode sheet is obtained.

5. The method for preparing an active slurry according to claim 4, characterized in that, Under the aforementioned vacuum condition, the vacuum level is 10. -2 Pa~10 -3 Pa.

6. The application of a positive electrode sheet as described in any one of claims 1 to 3 in electric vehicles, grid energy storage, industrial automation, and renewable energy systems.

Images