Zero-dimensional-one-dimensional composite positive electrode material and preparation method and application thereof

Abstract

The application provides a kind of zero-dimensional-one-dimensional composite positive electrode material and its preparation method and application, belong to battery positive electrode material field.The zero-dimensional-one-dimensional composite positive electrode material provided by the application includes nanoparticle positive electrode material and nanofiber positive electrode material;The mass ratio of the nanoparticle positive electrode material and nanofiber positive electrode material is 1: (0.2~1.5).The zero-dimensional-one-dimensional composite positive electrode material provided by the application is applied as active material in lithium ion battery positive electrode sheet, can make the first coulomb efficiency of half-cell reach 84.23%, with higher first coulomb efficiency;The specific capacity under 0.1C rate can reach 270.29mAhg ‑1 , with high specific capacity;The specific capacity under 8C high rate can still be kept at 82.03mAhg ‑1 , with excellent rate performance;Capacity retention rate can reach 86.68% after 300 cycles under 2C rate, with good cycle stability.

Description

Technical Field

[0001] This invention relates to the field of battery cathode materials, and more particularly to a zero-dimensional-one-dimensional composite cathode material, its preparation method, and its application. Background Technology

[0002] In the field of lithium-ion batteries, cathode materials can be prepared into nanofibers and nanoparticles to improve their electrochemical performance. However, one-dimensional nanofibers suffer from low tap density and volumetric energy density, complex synthesis processes, and high costs. Their larger specific surface area leads to more electrolyte decomposition under high voltage during the first charge cycle, resulting in low coulombic efficiency. During coating, the aspect ratio and toughness of the fibers may lead to poor rheological properties of the slurry, easy entanglement, and unevenness, making electrode processing difficult. On the other hand, zero-dimensional nanoparticles require lithium-ion transport to pass through countless particle-particle interfaces and grain boundaries with different orientations, increasing internal resistance and charge conduction resistance. Furthermore, the irreversible phase transitions and volume changes that occur in nanoparticle cathode materials during cycling generate stress that cannot be released within the hard particles, leading to microcracks and volumetric stress concentration, which reduces the battery's specific capacity, rate performance, and cycle stability. Summary of the Invention

[0003] The purpose of this invention is to provide a zero-dimensional-one-dimensional composite cathode material, its preparation method, and its applications. Half-cells prepared from cathode sheets obtained using the zero-dimensional-one-dimensional composite cathode material provided by this invention exhibit good rate performance, cycle stability, high specific capacity, and high initial coulombic efficiency.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a zero-dimensional-one-dimensional composite cathode material, including nanoparticle cathode materials and nanofiber cathode materials; The mass ratio of the nanoparticle cathode material to the nanofiber cathode material is 1:(0.2~1.5).

[0005] Preferably, the mass ratio of the nanoparticle cathode material to the nanofiber cathode material is 1:(0.8~1.5).

[0006] Preferably, the mass ratio of the nanoparticle cathode material to the nanofiber cathode material is 1:(1.0~1.2).

[0007] Preferably, the particle size of the nanoparticle cathode material is 50~300nm.

[0008] Preferably, the diameter of the nanofiber cathode material is 50~400nm and the aspect ratio is 50~200:1.

[0009] Preferably, the cathode material in the nanoparticle cathode material and the nanofiber cathode material is independently selected from one of lithium-rich manganese-based cathode materials, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0010] This invention also provides a method for preparing the zero-dimensional-one-dimensional composite cathode material described in the above technical solution, comprising: Nanoparticle cathode material, nanofiber cathode material and organic solvent are mixed and dried to obtain zero-dimensional-one-dimensional composite cathode material.

[0011] Preferably, the organic solvent includes one or more of anhydrous ethanol, N,N-dimethylpyrrolidone, and N-methylpyrrolidone.

[0012] Preferably, the mixing is carried out under stirring conditions; the stirring speed is 800~3000 rpm, and the stirring time is ≥24h.

[0013] This invention provides a positive electrode sheet for a lithium-ion battery, wherein the active material of the positive electrode sheet is the zero-dimensional-one-dimensional composite positive electrode material described in the above-mentioned technical solution or the zero-dimensional-one-dimensional composite positive electrode material prepared by the preparation method described in the above-mentioned technical solution. This invention provides a zero-dimensional to one-dimensional composite cathode material, comprising nanoparticle cathode material and nanofiber cathode material; the mass ratio of the nanoparticle cathode material to the nanofiber cathode material is 1:(0.2~1.5). By introducing nanoparticle cathode material, this invention significantly enhances the mechanical strength, thermal conductivity, and electrical conductivity of the one-dimensional nanofiber cathode material, while simultaneously improving the initial coulombic efficiency of the composite cathode material. The high specific surface area and microstructure of the nanofiber cathode material provide a uniformly distributed carrier for the nanoparticle cathode material, effectively preventing nanoparticle aggregation. Simultaneously, the fiber network anchors the particles, improving the overall mechanical stability of the material and thus enhancing the cycle performance of the cathode material. Adjusting the mass ratio of nanoparticle cathode material to nanofiber cathode material can further improve the specific capacity, rate performance, and cycle stability of the half-cell prepared from the composite cathode material.

[0014] The preparation method provided by this invention disperses and mixes nanoparticles and nanofibers using an organic solvent. This ensures thorough and uniform mixing while maximally preserving the original morphology and surface characteristics of the material, and the nanofibers are less prone to breakage. Example results show that the zero-dimensional-one-dimensional composite cathode material provided by this invention, when used as an active material in the cathode sheet of a lithium-ion battery, can achieve an initial coulombic efficiency of 84.23% for the lithium-ion half-cell, exhibiting high initial coulombic efficiency; the specific capacity at 0.1C rate can reach 270.29 mAh g⁻¹. -1 It exhibits high specific capacity; even at a high rate of 8C, the specific capacity remains at 82.03 mAh g.-1 It has excellent rate performance; after 300 cycles at 2C rate, the capacity retention can reach 86.68%, and it has good cycle stability. Attached Figure Description

[0015] Figure 1 This is a TEM image of the cathode material of Comparative Example 1 of the present invention; Figure 2 This is a TEM image of the cathode material of Comparative Example 2 of the present invention; Figure 3 The first charge-discharge curves and coulombic efficiency diagrams of half-cells prepared from the positive electrode sheets of lithium-ion batteries in Application Examples 1, 3 and Comparative Application Example 2 of this invention are shown. Figure 4 The cyclic voltammetry curve of the half-cell prepared from the positive electrode of the lithium-ion battery in Comparative Application Example 1 of the present invention is shown. Figure 5 The cyclic voltammetry curve of the half-cell prepared by the positive electrode of the lithium-ion battery in Application Example 1 of this invention is shown. Figure 6 The cyclic voltammetry curve of the half-cell prepared by the lithium-ion battery positive electrode sheet of Example 3 of the present invention is shown. Figure 7 The cyclic voltammetry curve of the half-cell prepared by the lithium-ion battery positive electrode sheet of Example 4 of this invention is shown. Figure 8 Electrochemical impedance spectroscopy of half-cells prepared from the positive electrode of a lithium-ion battery in Application Example 3 and Comparative Application Example 1 of this invention. Figure 9 The graphs show the cycle performance of half-cells prepared from the positive electrode sheets of lithium-ion batteries in Application Examples 2-4 and Comparative Application Example 1 at different rates. Figure 10 The graphs show the cycle performance of half-cells prepared from the positive electrode sheets of lithium-ion batteries in Application Examples 2-4 and Comparative Application Example 1 at a 2C rate. Detailed Implementation

[0016] This invention provides a zero-dimensional-one-dimensional composite cathode material, including nanoparticle cathode materials and nanofiber cathode materials.

[0017] In one embodiment of the present invention, the particle size of the nanoparticle cathode material can be 50-300 nm, 100-250 nm, or 150-200 nm. Limiting the particle size of the nanoparticle cathode material to the above range allows for better loading of nanoparticles onto the nanofiber cathode material.

[0018] In one embodiment of the present invention, the diameter of the nanofiber cathode material can be 50-400 nm, 150-350 nm, or 200-250 nm; the aspect ratio of the nanofiber cathode material can be 50-200:1, 100-150:1, or 120-130:1. Limiting the diameter and aspect ratio of the nanofiber cathode material to the above ranges allows for better loading of nanoparticles onto the nanofiber cathode material and more uniform mixing of nanoparticles and nanofibers.

[0019] In one embodiment of the present invention, the cathode material in the nanoparticle cathode material and the nanofiber cathode material can be independently selected from one of lithium-rich manganese-based cathode materials, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. In an embodiment of the present invention, the cathode material in both the nanoparticle cathode material and the nanofiber cathode material is Li. 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2.

[0020] In this invention, the mass ratio of the nanoparticle cathode material to the nanofiber cathode material is 1:(0.2~1.5), preferably 1:(0.8~1.5), more preferably 1:(0.9~1.3), further preferably 1:(1.0~1.2), and most preferably 1:1. Limiting the mass ratio of the nanoparticle cathode material to the nanofiber cathode material to the above range ensures thorough mixing of the two materials and results in half-cells prepared from the composite cathode material exhibiting higher specific capacity, initial coulombic efficiency, rate performance, and cycle stability.

[0021] This invention, by introducing nanoparticle cathode materials, can significantly enhance the mechanical strength, thermal conductivity, and electrical conductivity of one-dimensional nanofiber cathode materials, while simultaneously improving the initial coulombic efficiency of the composite cathode material. The high specific surface area and microstructure of the nanofiber cathode material provide a uniformly distributed carrier for the nanoparticle cathode material, effectively preventing nanoparticle aggregation. Furthermore, the fiber network anchors the particles, enhancing the overall mechanical stability of the material and improving the cycle performance of the half-cell prepared from the cathode material. By adjusting the mass ratio of nanoparticle cathode material to nanofiber cathode material, the specific capacity, rate performance, and cycle stability of the half-cell prepared from the composite cathode material can be further improved.

[0022] This invention also provides a method for preparing the zero-dimensional-one-dimensional composite cathode material described in the above technical solution, comprising: Nanoparticle cathode material, nanofiber cathode material and organic solvent are mixed and dried to obtain zero-dimensional-one-dimensional composite cathode material.

[0023] In one embodiment of the present invention, the organic solvent may include one or more of anhydrous ethanol, N,N-dimethylpyrrolidone, and N-methylpyrrolidone. In an embodiment of the present invention, the organic solvent is a mixture of anhydrous ethanol and N-methylpyrrolidone.

[0024] The present invention does not impose any particular limitation on the preparation method of the nanoparticle cathode material and the nanofiber cathode material. The nanoparticle cathode material and the nanofiber cathode material with the size specified in the above technical solution can be prepared by using methods commonly used by those skilled in the art.

[0025] As one embodiment of the present invention, the nanoparticle cathode material can be prepared by polymer network gelation.

[0026] As one embodiment of the present invention, the preparation of nanoparticle cathode materials by the polymer network gel method may specifically include: A gel is obtained by mixing a networking agent, a complexing agent, a metal salt, and a solvent and then carrying out a polymerization reaction. The gel was subjected to a first drying and calcination process to obtain a nanoparticle cathode material.

[0027] This invention allows for the polymerization reaction of a mixture of a networking agent, a complexing agent, a metal salt, and a solvent to obtain a gel.

[0028] In one embodiment of the present invention, the metal salt can be an acetate or nitrate of the corresponding metal contained in the nanoparticle cathode material. In an embodiment of the present invention, the metal salt is an acetate of the corresponding metal contained in the nanoparticle cathode material; the cathode material in the nanoparticle cathode material is Li. 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2, the corresponding metal acetates are lithium acetate, manganese acetate, cobalt acetate and nickel acetate; the molar ratio of lithium, manganese, cobalt and nickel in lithium acetate, manganese acetate, cobalt acetate and nickel acetate is 1.2:0.54:0.13:0.13.

[0029] In an embodiment of the present invention, the networking agent is a mixture of acrylamide and NN'-methylenebispropionamide; the mass ratio of acrylamide to NN'-methylenebispropionamide is 5:1; the complexing agent is citric acid; and the solvent is deionized water.

[0030] In embodiments of the present invention, the ratio of the total amount of metal ions in the metal salt to the amount of complexing agent is 1:1; the ratio of the amount of networking agent to complexing agent is 1:1 or 1.5:1.

[0031] In one embodiment of the present invention, the mixing can be carried out under stirring conditions; the mixing can be as follows: a first mixing of the networking agent with half a volume of solvent to obtain mixture A; a second mixing of the metal salt, complexing agent, and remaining solvent to obtain mixture B; and a third mixing of mixture A and mixture B. In another embodiment of the present invention, when mixing mixture A and mixture B are mixed for the third time, mixture B can be added to mixture A; the addition rate can be 10 mL / min.

[0032] In an embodiment of the present invention, the temperature of the first and second mixing is 45°C; the temperature of the third mixing is 60°C. In another embodiment of the present invention, after the third mixing, the temperature is further increased to 85°C, and stirring is stopped when the mixture begins to gel. The mixture is then kept at 85°C for 1 hour to obtain a gel.

[0033] After obtaining the gel, the present invention can sequentially perform a first drying and calcination on the gel to obtain a nanoparticle cathode material.

[0034] In one embodiment of the present invention, the gel can be broken up before the first drying. The present invention does not have specific limitations on the breaking up operation; any operation that can uniformly break the gel into small pieces is acceptable.

[0035] In one embodiment of the present invention, the first drying temperature can be 80~150℃ or 100~120℃. The present invention does not specifically limit the first drying time, as long as the gel is dried to a constant weight. In an embodiment of the present invention, the drying time is 24 hours.

[0036] In one embodiment of the present invention, the calcination can be carried out in an oxygen atmosphere or an air atmosphere; the calcination temperature can be 800~1000℃ or 850~900℃; the calcination time can be 8~15h or 10~12h; and the heating rate to the calcination temperature can be 4~6℃ / min or 5℃ / min. By limiting the calcination parameters to the above ranges, the present invention can obtain nanoparticle cathode materials with better performance.

[0037] In one embodiment of the present invention, the nanofiber cathode material can be prepared by electrospinning.

[0038] As one embodiment of the present invention, the preparation of nanofiber cathode materials by electrospinning may specifically include: Electrospinning was performed on a spinning solution obtained by mixing a metal salt, a polymer, and a first organic solvent to obtain a precursor for nanofiber cathode material. The nanofiber cathode material precursor was subjected to a second drying and low-temperature calcination in sequence to obtain the nanofiber cathode material.

[0039] As one embodiment of the present invention, a spinning solution obtained by mixing a metal salt, a polymer and a first organic solvent can be electrospun to obtain a nanofiber cathode material precursor.

[0040] In this invention, the range of metal salts selected in the preparation process of the nanofiber cathode material is the same as the range of metal salts selected in the preparation process of the nanoparticle cathode material described above, and will not be repeated here. In the embodiments of this invention, the metal salts selected in the preparation process of the nanofiber cathode material are the same as the metal salts selected in the preparation process of the nanoparticle cathode material described above, and will not be repeated here.

[0041] In one embodiment of the present invention, the polymer can be one or two of polyvinyl alcohol, polyvinylpyrrolidone, and polyacrylonitrile. Limiting the type of polymer to the above-mentioned range in the present invention is more conducive to spinning. In an embodiment of the present invention, the polymer is polyvinylpyrrolidone.

[0042] In one embodiment of the present invention, the first organic solvent may be one or two of anhydrous ethanol, N,N-dimethylpyrrolidone, and N-methylpyrrolidone, or it may be anhydrous ethanol and / or N,N-dimethylpyrrolidone. In an embodiment of the present invention, the first organic solvent is anhydrous ethanol.

[0043] In one embodiment of the present invention, the concentration of the metal salt in the spinning solution can be 5-15 wt%, 8-12 wt%, or 10 wt%. By limiting the concentration of the metal salt in the spinning solution to the above range, the present invention can ensure smooth spinning while loading sufficient positive active material onto the fiber.

[0044] In one embodiment of the present invention, the concentration of the polymer in the spinning solution can be 6-18 wt%, 8-15 wt%, 10-13 wt%, or 11-12 wt%. The present invention limits the concentration of the polymer in the spinning solution to the above ranges to form high-quality nanofibers.

[0045] As one embodiment of the present invention, the mixing of the metal salt, the polymer and the first organic solvent can be: first, the polymer and the first organic solvent are mixed in a fourth step, and then the metal salt is added for a fifth step of mixing.

[0046] In one embodiment of the present invention, the fourth and fifth mixing are carried out under stirring conditions. The present invention does not impose any particular limitation on the stirring speed of the fourth and fifth mixing, as long as it avoids powder agglomeration, powder splashing, and the generation of bubbles.

[0047] In one embodiment of the present invention, the electrospinning voltage can be 12~21.5kV, 13~20kV, 14~18kV, or 16~18kV; the electrospinning feed speed can be 1.5~4mL / h or 2~3mL / h; the electrospinning receiving distance can be 13~21cm or 15cm; the fiber collecting drum rotation speed can be >200rpm, 200~500rpm, or 200~300rpm; the ambient humidity for electrospinning can be <50%, 25~50%, or 35~40%. Limiting the electrospinning parameters to the above ranges allows for better acquisition of nanofibers.

[0048] In one embodiment of the present invention, after the electrospinning is completed, the nanofibers on the fiber collecting drum can be removed to obtain a nanofiber cathode material precursor.

[0049] After obtaining the nanofiber cathode material precursor, the present invention can sequentially perform a second drying and low-temperature calcination on the nanofiber cathode material precursor to obtain the nanofiber cathode material.

[0050] The present invention does not have any special limitations on the temperature and time of the second drying process; it is sufficient to dry the nanofiber cathode material precursor to a constant weight.

[0051] In one embodiment of the present invention, the low-temperature calcination can be carried out in a tubular furnace; the low-temperature calcination can be carried out in an oxygen atmosphere; the low-temperature calcination temperature can be 650~850℃ or 700~800℃; the low-temperature calcination time can be 8~12h or 8~10h. In another embodiment of the present invention, during the heating process of the low-temperature calcination, the heating rate before 400℃ can be 4~5℃ / min, and the heating rate after 400℃ can be 2~3℃ / min. By limiting the temperature, time, and heating rate of the low-temperature calcination to the above ranges, the present invention can obtain nanofiber cathode materials with good performance.

[0052] As one embodiment of the present invention, the low-temperature calcination process can be carried out by holding at 400°C for 2 hours to completely remove residual organic solvents and moisture, maintain fiber morphology, and decompose and remove polymers.

[0053] In one embodiment of the present invention, the mass ratio of the nanoparticle cathode material to the nanofiber cathode material is consistent with the mass ratio of the nanoparticle cathode material to the nanofiber cathode material in the composite cathode material; the mass ratio of the nanoparticle cathode material to the volume ratio of the organic solvent can be (5~10) g: 50 mL, (6~9) g: 50 mL, or (7~8) g: 50 mL. Limiting the mass ratio of the nanoparticle cathode material to the volume ratio of the organic solvent to the above range allows for better uniform dispersion of the nanoparticle cathode material and the nanofiber cathode material in the organic solvent.

[0054] In one embodiment of the present invention, the mixing of the nanoparticle cathode material, the nanofiber cathode material, and the organic solvent can be carried out in a closed container; the mixing of the nanoparticle cathode material, the nanofiber cathode material, and the organic solvent can be carried out under stirring conditions; the stirring speed can be 800~3000 rpm or 1000~2000 rpm; the stirring time can be ≥24h or 24~28h. The present invention limits the mixing parameters to the above ranges to ensure that the nanoparticle cathode material and the nanofiber cathode material are sufficiently and uniformly mixed.

[0055] In one embodiment of the present invention, the drying temperature can be 75~150℃ or 80~120℃; the drying time can be 1.5~8h or 2~4h. By limiting the drying temperature and time to the above ranges, the present invention can sufficiently dry the composite cathode material.

[0056] The present invention also provides a positive electrode sheet for a lithium-ion battery, wherein the active material of the positive electrode sheet is the zero-dimensional-one-dimensional composite positive electrode material described in the above technical solution or the zero-dimensional-one-dimensional composite positive electrode material prepared by the preparation method described in the above technical solution.

[0057] As one embodiment of the present invention, the method for preparing the positive electrode sheet of the lithium-ion battery includes: A slurry is obtained by mixing zero-dimensional and one-dimensional composite cathode material, binder and conductive agent, and then adding N-methylpyrrolidone. The slurry is coated on aluminum foil and dried, then rolled flat and cut to obtain lithium-ion battery cathode sheet.

[0058] In a specific application example of the present invention, the mass ratio of the zero-dimensional to one-dimensional composite cathode material, binder, and conductive agent is 8:1:1; the solid content of the slurry is 48%.

[0059] In one embodiment of the present invention, the drying process may involve first drying at 60°C for 2-6 hours, and then drying at 120°C for more than 12 hours in a vacuum drying oven.

[0060] In a specific application example of the present invention, the positive electrode of the lithium-ion battery is a circular sheet with a diameter of 12 mm.

[0061] In a specific application example of the present invention, after obtaining the positive electrode sheet of the lithium-ion battery, the positive electrode sheet can be dried again; the re-drying is carried out in a vacuum drying oven; the re-drying temperature is 120°C. The present invention does not have a special limitation on the re-drying time; the lithium-ion battery positive electrode sheet can be dried to a constant weight.

[0062] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0063] Example 1 A zero-dimensional-one-dimensional composite cathode material is composed of nanoparticle cathode material and nanofiber cathode material; The mass ratio of the nanoparticle cathode material to the nanofiber cathode material is 1:0.2; The cathode material in both the nanoparticle cathode material and the nanofiber cathode material is Li. 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2; The particle size of the nanoparticle cathode material is 250 nm; the diameter of the nanofiber cathode material is 200 nm, and the aspect ratio of the nanofiber cathode material is 120:1. The preparation method of the zero-dimensional-one-dimensional composite cathode material is as follows: Nanoparticle cathode material, nanofiber cathode material, and organic solvent (anhydrous ethanol and N-methylpyrrolidone mixed in a volume ratio of 4:1) were stirred at 2000 rpm for 24 hours to achieve uniform mixing. The mixture was then dried in an oven at 80°C for 2 hours to obtain a zero-dimensional-one-dimensional composite cathode material. The mass ratio of the nanoparticle cathode material to the nanofiber cathode material was 1:0.2; the mass ratio of the nanoparticle cathode material to the volume ratio of the organic solvent was 8 g:50 mL. The nanoparticle cathode material was prepared by a polymer network gel method, specifically: A mixture of a networking agent (a mixture of acrylamide and NN'-methylenebispropionamide, with a mass ratio of acrylamide to NN'-methylenebispropionamide of 5:1) and half of deionized water was first mixed in a 45°C water bath to fully dissolve the networking agent, yielding mixture A. A complexing agent (citric acid, with a total molar ratio of metal ions in the metal salt to the total molar ratio of the complexing agent of 1:1, and a molar ratio of networking agent to complexing agent of 1.5:1) was then mixed with a metal salt (lithium acetate, manganese acetate, cobalt acetate, and nickel acetate). A mixture of lithium, manganese, cobalt, and nickel in a molar ratio of 1.2:0.54:0.13:0.13 and half of deionized water was stirred in a water bath at 45°C to completely dissolve the metal salts, resulting in a mixture B. Mixture B was then slowly poured into mixture A along the inner wall of a beaker at a rate of 10 mL / min. A third mixing was performed in a water bath at 60°C, and the temperature was further increased to 85°C with continuous stirring. Stirring was stopped when the mixture began to gel, and the mixture was kept at 85°C for 1 hour to obtain a gel. The gel was crushed and dried in an oven at 120°C for 24 hours, and then calcined at 850°C for 10 hours (oxygen atmosphere) with the temperature increased at 5°C / min to obtain nanoparticle cathode material. The nanofiber cathode material is prepared by electrospinning, specifically as follows: A fourth step involves mixing a metal salt and anhydrous ethanol, followed by adding polyvinylpyrrolidone (PVP) for a fifth step. The mixture is then stirred for 12 hours until PPVP is completely dissolved, yielding a spinning solution. This spinning solution is then injected into a syringe for electrospinning (the electrospinning voltage is 18 kV, the electrospinning feed rate is 3 mL / h, the electrospinning receiving distance is 15 cm, the electrospinning fiber collecting drum rotation speed is 250 rpm, and the ambient humidity is 38%). The nanofibers are then removed from the fiber collecting drum to obtain a nanofiber cathode material precursor. The concentration of the metal salt in the spinning solution is 8 wt%, and the concentration of the polymer in the spinning solution is 10 wt%. After drying the nanofiber cathode material precursor to constant weight at 80°C, it was pre-oxidized in a tube furnace at 400°C at 5°C / min for 2 hours, and then calcined at 800°C at 2°C / min for 8 hours (oxygen atmosphere). After natural cooling, the nanofiber cathode material was obtained.

[0064] Example 2 The only difference between Example 2 and Example 1 is that the mass ratio of nanoparticle cathode material to nanofiber cathode material in the zero-dimensional-one-dimensional composite cathode material is 1:0.6, and the mass ratio of nanoparticle cathode material to nanofiber cathode material in the preparation method of the zero-dimensional-one-dimensional composite cathode material is 1:0.6. The rest is the same as in Example 1.

[0065] Example 3 The only difference between Example 3 and Example 1 is that the mass ratio of nanoparticle cathode material to nanofiber cathode material in the zero-dimensional-one-dimensional composite cathode material is 1:1, and the mass ratio of nanoparticle cathode material to nanofiber cathode material in the preparation method of the zero-dimensional-one-dimensional composite cathode material is 1:1. All other aspects are the same as in Example 1.

[0066] Example 4 The only difference between Example 4 and Example 1 is that the mass ratio of nanoparticle cathode material to nanofiber cathode material in the zero-dimensional-one-dimensional composite cathode material is 1:1.5, and the mass ratio of nanoparticle cathode material to nanofiber cathode material in the preparation method of the zero-dimensional-one-dimensional composite cathode material is 1:1.5. All other aspects are the same as in Example 1.

[0067] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that no nanofiber cathode material is added, and only nanoparticle cathode material is contained. Otherwise, they are the same as Example 1.

[0068] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that no nanoparticle cathode material is added, and only nanofiber cathode material is contained. Otherwise, they are the same as Example 1.

[0069] Application Example 1 A positive electrode sheet for a lithium-ion battery, wherein the active material of the positive electrode sheet is the zero-dimensional-one-dimensional composite positive electrode material described in Example 1; The method for preparing the positive electrode sheet of the lithium-ion battery is as follows: Zero-dimensional-one-dimensional composite cathode material, binder (polyvinylidene fluoride), and conductive agent (superconducting carbon black Super-P) were ground in a mass ratio of 8:1:1, and then N-methylpyrrolidone was added to obtain a slurry with a solid content of 48%. The slurry was then uniformly coated (coating amount of 10 mg / cm²). 2 The aluminum foil is first dried at 60°C for 2 hours, then dried at 120°C for 12 hours in a vacuum drying oven. After being rolled flat, it is cut to obtain the positive electrode sheet of lithium-ion battery (a round sheet with a diameter of 12 mm). The positive electrode sheet of lithium-ion battery is then dried again in a vacuum drying oven at 120°C until it reaches a constant weight for later use.

[0070] Application Example 2 The only difference between Application Example 2 and Application Example 1 is that the active material of the positive electrode of the lithium-ion battery is the zero-dimensional-one-dimensional composite positive electrode material described in Example 2; otherwise, they are the same as in Application Example 1.

[0071] Application Example 3 The only difference between Application Example 3 and Application Example 1 is that the active material of the positive electrode of the lithium-ion battery is the zero-dimensional-one-dimensional composite positive electrode material described in Example 3; otherwise, they are the same as in Application Example 1.

[0072] Application Example 4 The only difference between Application Example 4 and Application Example 1 is that the active material of the positive electrode of the lithium-ion battery is the zero-dimensional-one-dimensional composite positive electrode material described in Example 4; otherwise, they are the same as in Application Example 1.

[0073] Comparative Application Example 1 The only difference between Comparative Example 1 and Application Example 2 is that the active material of the positive electrode of the lithium-ion battery is the positive electrode material described in Comparative Example 1; otherwise, they are the same as in Application Example 1.

[0074] Comparative Application Example 2 The only difference between Application Example 2 and Application Example 1 is that the active material of the positive electrode of the lithium-ion battery is the positive electrode material described in Comparative Example 2; otherwise, they are the same as in Application Example 1.

[0075] Test case The cathode materials of Comparative Example 1 and Comparative Example 2 were observed using transmission electron microscopy. The TEM image of the cathode material prepared in Comparative Example 1 is shown below. Figure 1 As shown, the TEM image of the cathode material prepared in Comparative Example 2 is as follows. Figure 2 As shown. From Figures 1-2 As can be seen, nanoparticles have a zero-dimensional morphology, while nanofibers have a one-dimensional morphology.

[0076] Lithium metal sheets were selected as the counter electrode, and (1M LiPF6 / EC+DMC+EMC (volume ratio 1:1:1); ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC)) was selected as the electrolyte. Celgard series separators were selected. In a glove box protected by an inert atmosphere (high-purity argon), CR2032 button cells (half cells) were assembled in the following order from bottom to top: positive electrode shell, lithium-ion battery positive electrode sheet, electrolyte, separator, electrolyte, lithium sheet, gasket, spring sheet, and negative electrode shell. The cells were sealed with a sealing machine and tested using the Xinwei Battery Testing System after being left to stand for 24 hours.

[0077] The first charge-discharge curves and coulombic efficiency diagrams of the half-cells prepared from the lithium-ion battery positive electrode sheets of Application Example 1, Application Example 3, and Comparative Application Example 2 are shown below. Figure 3 As shown, from Figure 3As can be seen, the discharge specific capacity of the batteries prepared by the lithium-ion battery positive electrode sheets of Application Example 1 and Application Example 3 is higher than that of the battery prepared by the lithium-ion battery positive electrode sheet of Comparative Application Example 2. The three have similar charge and discharge platforms. The coulombic efficiency of the batteries prepared by the lithium-ion battery positive electrode sheets of Application Example 1 and Application Example 3 is higher than that of the half-cell prepared by the lithium-ion battery positive electrode sheet of Comparative Application Example 2. Moreover, the coulombic efficiency of the battery prepared by the lithium-ion battery positive electrode sheet of Application Example 3 is the highest, reaching 84.23%, and has a high initial coulombic efficiency.

[0078] The cyclic voltammograms of the half-cell prepared by comparing the lithium-ion battery positive electrode sheet of Application Example 1 are shown below. Figure 4 As shown, the cyclic voltammetry curve of the half-cell prepared using the lithium-ion battery positive electrode sheet of Example 1 is as follows. Figure 5 As shown, the cyclic voltammetry curve of the half-cell prepared using the lithium-ion battery positive electrode sheet of Example 3 is as follows. Figure 6 As shown, the cyclic voltammetry curve of the half-cell prepared using the lithium-ion battery positive electrode sheet of Example 4 is as follows. Figure 7 As shown, from Figures 4-7 As can be seen, the batteries prepared using the lithium-ion battery positive electrode sheets of Application Examples 1, 3, and 4 have better cycle stability than the batteries prepared using the lithium-ion battery positive electrode sheet of Comparative Application Example 1.

[0079] The electrochemical impedance spectroscopy spectra of the half-cells prepared from the positive electrode of the lithium-ion battery in Application Example 3 and Comparative Application Example 1 are as follows: Figure 8 As shown, from Figure 8 As can be seen, the resistance of the battery prepared using the lithium-ion battery positive electrode sheet of Example 3 is less than that of the battery prepared using the lithium-ion battery positive electrode sheet of Example 1.

[0080] Half-cells prepared from the lithium-ion battery positive electrode sheets corresponding to Application Examples 2-4 and Comparative Application Example 1 were tested for rate performance. The cycle performance curves of the half-cells prepared from the lithium-ion battery positive electrode sheets of Application Examples 2-4 and Comparative Application Example 1 at different rates are shown in the figure below. Figure 9 As shown, from Figure 9 It can be seen that the specific capacity at a 0.1C rate can reach 270.29 mAh g. -1 Even at a high rate of 8C, the specific capacity can still reach 82.03 mAh g. -1 The battery prepared using the lithium-ion battery positive electrode sheet of Example 3 has a more stable platform and higher capacity at various rates. The batteries prepared using the lithium-ion battery positive electrode sheets of Examples 2 to 4 all have better rate performance than the batteries prepared using the lithium-ion battery positive electrode sheet of Example 1.

[0081] The half-cells prepared from the lithium-ion battery positive electrode sheets corresponding to Application Examples 2-4 and Comparative Application Example 1 were tested for cycle performance at 2C rate. The cycle performance curves of the half-cells prepared from the lithium-ion battery positive electrode sheets of Application Examples 2-4 and Comparative Application Example 1 at 2C rate are shown in the figure below. Figure 10 As shown, from Figure 10 It can be seen that the batteries prepared using the lithium-ion battery positive electrode sheets of Examples 2 to 4 all have higher discharge specific capacity and better cycle stability than the batteries prepared using the lithium-ion battery positive electrode sheet of Example 1. After 300 cycles at 2C rate, the capacity retention rate can reach 86.68%.

[0082] The zero-dimensional-one-dimensional composite cathode material provided by this invention, when used as an active material in the cathode sheet of lithium-ion batteries, can achieve an initial coulombic efficiency of 84.23% for lithium-ion half-cells, exhibiting high initial coulombic efficiency; the specific capacity at 0.1C rate can reach 270.29 mAh g⁻¹. -1 It exhibits high specific capacity; even at a high rate of 8C, the specific capacity remains at 82.03 mAh g. -1 It has excellent rate performance; after 300 cycles at 2C rate, the capacity retention can reach 86.68%, and it has good cycle stability.

[0083] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A zero-dimensional-one-dimensional composite cathode material, comprising nanoparticle cathode material and nanofiber cathode material; The mass ratio of the nanoparticle cathode material to the nanofiber cathode material is 1:(0.2~1.5).

2. The zero-dimensional-one-dimensional composite cathode material according to claim 1, characterized in that, The mass ratio of the nanoparticle cathode material to the nanofiber cathode material is 1:(0.8~1.5).

3. The zero-dimensional-one-dimensional composite cathode material according to claim 2, characterized in that, The mass ratio of the nanoparticle cathode material to the nanofiber cathode material is 1:(1.0~1.2).

4. The zero-dimensional-one-dimensional composite cathode material according to any one of claims 1 to 3, characterized in that, The particle size of the nanoparticle cathode material is 50~300nm.

5. The zero-dimensional-one-dimensional composite cathode material according to any one of claims 1 to 3, characterized in that, The diameter of the nanofiber cathode material is 50~400nm, and the aspect ratio is 50~200:

1.

6. The zero-dimensional-one-dimensional composite cathode material according to any one of claims 1 to 3, characterized in that, The cathode material in the nanoparticle cathode material and the nanofiber cathode material is independently selected from one of lithium-rich manganese-based cathode materials, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

7. A method for preparing the zero-dimensional-one-dimensional composite cathode material according to any one of claims 1 to 6, comprising: Nanoparticle cathode material, nanofiber cathode material and organic solvent are mixed and dried to obtain zero-dimensional-one-dimensional composite cathode material.

8. The preparation method according to claim 7, characterized in that, The organic solvent includes one or more of anhydrous ethanol, N,N-dimethylpyrrolidone, and N-methylpyrrolidone.

9. The preparation method according to claim 7, characterized in that, The mixing is carried out under stirring conditions; the stirring speed is 800~3000 rpm, and the stirring time is ≥24h.

10. A positive electrode sheet for a lithium-ion battery, characterized in that, The active material of the positive electrode sheet of the lithium-ion battery is the zero-dimensional-one-dimensional composite positive electrode material according to any one of claims 1 to 6 or the zero-dimensional-one-dimensional composite positive electrode material prepared by the preparation method according to any one of claims 7 to 9.

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