A positive electrode sheet, a battery, and an electric device
By setting first and second cathode material layers in the cathode sheet, controlling the binder content and particle size, and optimizing the binder specific gravity, the problems of brittleness and powder shedding of cathode sheets in dry processes are solved, achieving a balance between high energy density and good electrochemical performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- GUANGZHOU AUTOMOBILE GROUP CO LTD
- Filing Date
- 2026-03-26
- Publication Date
- 2026-06-05
AI Technical Summary
Existing cathode sheets are prone to brittleness and powder shedding during dry process preparation due to insufficient flexibility, and increasing the binder dosage will reduce the proportion of active material and the electrochemical performance of the battery.
By setting first and second positive electrode material layers in the positive electrode sheet, controlling the binder content and particle size range, and satisfying the relationship 1.5≤(C1D(2.2-S1)/(C2d(2.2-S2)≤5, the specific gravity and particle size ratio of the binder are optimized, and polytetrafluoroethylene binders are used in combination with conductive agents to construct an electronic conduction network.
It improves the overall flexibility and mechanical strength of the positive electrode, avoids brittleness and powder shedding, ensures the energy density and cycle performance of the battery, and improves electron conduction efficiency and battery life.
Smart Images
Figure CN122158472A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of battery technology, and more particularly to a positive electrode, a battery, and an electrical device. Background Technology
[0002] Lithium-ion batteries, as core energy storage devices in the new energy field, are widely used in power batteries, energy storage batteries, and other scenarios. Improving their performance and optimizing their manufacturing processes have always been key research areas in the industry. When positive electrode sheets are manufactured using dry processes, they are prone to brittleness and powder shedding during processing due to insufficient flexibility. Existing technologies avoid this by increasing the amount of binder added; however, excessive binder content reduces the proportion of active material, lowers energy density, and affects the battery's electrochemical performance.
[0003] Therefore, there is an urgent need to develop a positive electrode that can take into account both the mechanical properties of the electrode and the electrical properties of the battery. Summary of the Invention
[0004] This application provides a positive electrode, a battery, and an electrical device, aiming to improve the mechanical properties of existing positive electrode sheets and the electrical properties of batteries.
[0005] In a first aspect, this application provides a positive electrode sheet, including a current collector, a first positive electrode material layer, and a second positive electrode material layer. The first positive electrode material layer is disposed on at least one side of the current collector, and the second positive electrode material layer is disposed on the side of the first positive electrode material layer opposite to the current collector. The first positive electrode material layer includes a first active material and a first binder, and the second positive electrode layer includes a second active material and a second binder. The positive electrode plate satisfies the following relationship: 1.5≤(C1 D (2.2-S1) / (C2 d (2.2-S2)≤5, Wherein, the mass content of the first binder in the first positive electrode material layer is C1%, and the mass content of the second binder in the second positive electrode material layer is C2%; 1%≤C1%≤5%, 2%≤C2%≤10%; The D50 of the first active substance is Dμm, and the D50 of the second active substance is dμm; The standard specific gravity of the first adhesive is S1, and the standard specific gravity of the second adhesive is S2.
[0006] In this application, the limitation of the binder content range and the relational expression parameters act synergistically to effectively improve the overall flexibility and mechanical strength of the first positive electrode material layer and the second positive electrode material layer, avoid brittle fracture and powder shedding during dry processing, ensure good processing performance of the positive electrode sheet and the energy density of the battery, and improve the cycle performance of the battery. The first binder content in the first positive electrode material layer close to the current collector is controlled at 1% - 5%, which can ensure the proportion of the first active material in the first positive electrode material layer, avoid excessive binder occupying the space of the active material, and at the same time meet the basic binding requirements of the first positive electrode material layer, and ensure the bonding strength between the first positive electrode material layer and the current collector and between the first positive electrode material layer and the second positive electrode material layer; the binder content in the second positive electrode material layer is controlled at 2% - 10%, which can directly improve the flexibility and bonding strength of the surface of the electrode sheet, realize the improvement of the overall flexibility and mechanical strength of the two positive electrode material layers, resist the mechanical stress during dry rolling, cutting, and winding, reduce brittle fracture and powder shedding, and ensure the integrity and stability of the positive electrode sheet during processing.
[0007] The relational expression further optimizes the matching degree of the structures of the first positive electrode material layer and the second positive electrode material layer, ensures the smoothness of the ion conduction channels in the first positive electrode material layer and the second positive electrode material layer, reduces the hindrance of the binder to ion migration, and realizes the dual consideration of processing performance and electrical performance. In the relational expression, the terms (2.2 - S1) and (2.2 - S2) are related to the binder proportion. The smaller the proportion, the better the flexibility of the binder molecular chain. Combined with the binder content and particle size, the synergistic optimization of "bonding strength - ion conduction - particle packing" can be achieved, improving the overall flexibility and mechanical strength of the positive electrode sheet, ensuring processing performance, and at the same time further improving the energy density and cycle performance of the battery.
[0008] Optionally, in the positive electrode sheet, 0.1 < d / D < 0.8. That is, the particle size of the first active material is larger than that of the second active material, and the particle sizes of the active materials in the first positive electrode material layer and the second positive electrode material layer show a gradient change. By further limiting the ratio between the particle sizes of the first active material and the second active material, the distribution of lithium ions during battery operation is effectively optimized, the concentration polarization phenomenon is reduced, and thus the capacity release ability of the battery under high load conditions is significantly improved, making the battery have better rate performance and cycle stability. If d / D ≤ 0.1, the particles of the second active material in the second positive electrode material layer are too small and easy to agglomerate, resulting in blocked ion conduction, and the agglomerates are easy to fall off from the surface of the electrode sheet, affecting processing performance and product yield; if d / D ≥ 0.8, the particle size difference between the first active material and the second active material is too small to achieve effective packing, which not only affects the energy density but also causes a decrease in the overall flexibility and mechanical strength of the positive electrode sheet, and brittle fracture is easy to occur during processing, affecting processing performance.
[0009] Optionally, 5 ≤ D ≤ 20, 0.1 ≤ d ≤ 10. Within this range, the particle size of the first active material in the first positive electrode material layer can form a loose but stable framework structure, providing ample channels for ion migration. Within this range, the particle size of the second active material in the second positive electrode material layer can fill the gaps between the first active materials at the interface between the first and second positive electrode material layers, increasing the overall density of the electrode sheet, thereby improving the effective utilization rate of the active material and the battery energy density. Furthermore, within the aforementioned range, the particle size of the second active material has a larger specific surface area, resulting in a higher contact area with the second binder, forming a stronger bonding network, improving the mechanical strength of the positive electrode sheet, and reducing brittleness and powder shedding during processing.
[0010] Optionally, 2.12≤S1≤2.19, 2.12≤S2≤2.19. By limiting the standard specific gravity range of the first binder and the second binder, it is ensured that the first binder and the second binder have suitable molecular chain flexibility and density. In conjunction with the limited content range of the first binder and the second binder and the relationship formula, a stable bonding network is formed, which further improves the overall flexibility and mechanical strength of the positive electrode sheet, ensures good processing performance of the positive electrode sheet, avoids the obstruction of ion conduction due to excessively dense molecular chains, and adapts to the fibrillation process in dry preparation, indirectly optimizing processing efficiency.
[0011] Optionally, the first adhesive includes at least one of polytetrafluoroethylene and polytetrafluoroethylene derivatives; The second binder includes at least one of polytetrafluoroethylene (PTFE) and PTFE derivatives. The first and second binders are PTFE-based binders, which are suitable for the solvent-free characteristics of the dry preparation process. Furthermore, their excellent high-temperature resistance, electrolyte corrosion resistance, and high bonding strength further improve the mechanical stability and safety of the positive electrode sheet, thereby increasing the cycle life of the battery.
[0012] Optionally, the thickness of the first positive electrode material layer is 10-150 μm, and the thickness of the second positive electrode material layer is 10-150 μm. By limiting the thickness range of the first and second positive electrode material layers, the energy density, mechanical properties, and ion conductivity of the positive electrode sheet can be controlled within a suitable range, further improving the energy density and rate performance of the battery.
[0013] Optionally, the first active material includes at least one of monocrystalline particles and polycrystalline particles, and the second active material includes at least one of monocrystalline particles and polycrystalline particles. The combined use of monocrystalline and polycrystalline particles further improves the energy density of the battery.
[0014] Optionally, the first positive electrode material layer further includes a first conductive agent, and the second positive electrode material layer further includes a second conductive agent; The first conductive agent includes at least one of Ketjen black, graphite, hard carbon, soft carbon, carbon nanotubes, graphene, porous carbon, superconducting carbon black, acetylene black, furnace black, and whisker carbon nanotubes. The second conductive agent includes at least one of Ketjen black, graphite, hard carbon, soft carbon, carbon nanotubes, graphene, porous carbon, superconducting carbon black, acetylene black, furnace black, and whisker carbon nanotubes. By adding the first and second conductive agents, a continuous electron conduction network is constructed in the positive electrode, thereby improving the electron conduction efficiency of the electrode.
[0015] Secondly, this application provides a battery including the aforementioned positive electrode sheet. By selecting the aforementioned positive electrode sheet, the energy density of the battery is improved, and the cycle stability of the battery is enhanced. It should be noted that the battery can be a stacked or wound battery.
[0016] Thirdly, this application provides an electrical device including the battery described above. By using the battery with high energy density and good cycle stability, the battery life of the electrical device is improved. Attached Figure Description
[0017] Figure 1 This is a schematic diagram of the structure of a positive electrode sheet provided in an embodiment of this application; Figure 2 This is an electron microscope image of a cross-section of a positive electrode sheet provided in Embodiment 1 of this application.
[0018] Explanation of reference numerals in the attached figures: 1. Current collector; 2. First positive electrode material layer; 3. Second positive electrode material layer. Detailed Implementation
[0019] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.
[0020] like Figure 1 As shown, one embodiment of this application provides a positive electrode sheet, including a current collector 1, a first positive electrode material layer 2, and a second positive electrode material layer 3. The first positive electrode material layer 2 is disposed on at least one side of the current collector 1, and the second positive electrode material layer 3 is disposed on the side of the first positive electrode material layer 2 opposite to the current collector 1. The first positive electrode material layer 2 includes a first active material and a first binder, and the second positive electrode material layer 3 includes a second active material and a second binder. The positive electrode plate satisfies the following relationship: 1.5≤(C1 D (2.2-S1) / (C2 d (2.2-S2)≤5, Wherein, the mass content of the first binder in the first positive electrode material layer 2 is C1%, and the mass content of the second binder in the second positive electrode material layer 3 is C2%; 1%≤C1%≤5%, 2%≤C2%≤10%; The D50 of the first active substance is Dμm, and the D50 of the second active substance is dμm; The standard specific gravity of the first adhesive is S1, and the standard specific gravity of the second adhesive is S2.
[0021] In this embodiment, the limiting range of binder content and the synergistic effect of the relational parameters can effectively improve the overall flexibility and mechanical strength of the first positive electrode material layer 2 and the second positive electrode material layer 3, avoiding brittleness and powder shedding during dry processing, ensuring good processing performance of the positive electrode sheet and energy density of the battery, and improving the cycle performance of the battery. The content of the first binder in the first positive electrode material layer 2 near the current collector 1 is controlled at 1%-5%, which can ensure the proportion of the first active material in the first positive electrode material layer 2, avoid excessive space occupation of the active material due to excessive binder, and at the same time meet the basic bonding requirements of the first positive electrode material layer 2, ensuring the bonding strength between the first positive electrode material layer 2 and the current collector 1, and between the first positive electrode material layer 2 and the second positive electrode material layer 3; the binder content of the second positive electrode material layer 3 is controlled at 2%-10%, which can directly improve the flexibility and bonding strength of the electrode surface, realize the improvement of the overall flexibility and mechanical strength of the two positive electrode material layers, resist the mechanical stress during dry calendering, cutting, and winding, reduce brittleness and powder shedding, and ensure the integrity and stability of the positive electrode sheet during processing.
[0022] The formula further optimizes the matching degree of the structure of the first cathode material layer 2 and the second cathode material layer 3, ensuring unobstructed ion conduction channels in the first cathode material layer 2 and the second cathode material layer 3, reducing the obstruction of ion migration by the binder, and achieving a balance between processing performance and electrical performance. In the formula, terms (2.2-S1) and (2.2-S2) are related to the binder specific gravity. The lower the specific gravity, the better the flexibility of the binder molecular chain. Combined with the binder content and particle size, it can achieve synergistic optimization of "bonding strength-ion conduction-particle stacking", improve the overall flexibility and mechanical strength of the cathode sheet, ensure processing performance, and further improve the energy density and cycle performance of the battery.
[0023] Specifically, the mass content of the first adhesive includes, but is not limited to, any one value or a range of any two values from 1%, 2%, 3%, 4%, and 5%.
[0024] The mass content of the second adhesive includes, but is not limited to, any one value or a range of any two values from 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, and 10%.
[0025] In some embodiments, C1 and C2 can be detected by X-ray fluorescence spectrometry (XRF).
[0026] D50 is the median particle size of the active material particles, that is, the particle diameter when the cumulative particle size distribution reaches 50%, which is obtained by detecting with a laser particle size analyzer.
[0027] In some embodiments, in the positive electrode sheet, 0.1 < d / D < 0.8. That is, the particle size of the first active material is larger than that of the second active material, and the particle sizes of the active materials in the first positive electrode material layer 2 and the second positive electrode material layer 3 show a gradient change. By further limiting the ratio between the particle sizes of the first active material and the second active material, the distribution of lithium ions during the operation of the battery is effectively optimized, the concentration polarization phenomenon is reduced, and thus the capacity release ability of the battery under high load conditions is significantly improved, making the battery have better rate performance and cycle stability. If d / D ≤ 0.1, the particles of the second active material in the second positive electrode material layer 3 are too small and prone to agglomeration, resulting in blocked ion conduction, and the agglomerates are prone to fall off from the surface of the electrode sheet, affecting the processing performance and product yield; if d / D ≥ 0.8, the particle size difference between the first active material and the second active material is too small to achieve effective packing, which not only affects the energy density, but also causes the overall flexibility and mechanical strength of the positive electrode sheet to decrease, and it is prone to brittle cracking during the processing, affecting the processing performance.
[0028] In a preferred embodiment, 0.3 ≤ d / D ≤ 0.7, and more preferably, 0.4 ≤ d / D ≤ 0.6.
[0029] In some embodiments, 5 ≤ D ≤ 20, 0.1 ≤ d ≤ 10. The particle size of the first active material in the first positive electrode material layer 2 is within this range, which can form a loose but stable framework structure, providing sufficient channels for ion migration. The particle size of the second active material in the second positive electrode material layer 3 is within this range, which can fill the gaps between the first active materials at the junction of the first positive electrode material layer 2 and the second positive electrode material layer 3, improving the overall density of the electrode sheet, and further improving the effective utilization rate of the active material and the battery energy density; the particle size of the second active material is within the above range, having a larger specific surface area and a higher contact area with the second binder, which can form a more firm bonding network, improve the mechanical strength of the positive electrode sheet, and reduce brittle cracking and powder falling during the processing.
[0030] Specifically, the D50 of the first active material includes but is not limited to any point value or range value composed of any two point values among 5 μm, 7 μm, 9 μm, 11 μm, 13 μm, 15 μm, 17 μm, 19 μm, 20 μm.
[0031] The D50 of the second active substance includes, but is not limited to, any single value or a range of any two values from 0.1μm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, and 10μm.
[0032] In some embodiments, 2.12 ≤ S1 ≤ 2.19, 2.12 ≤ S2 ≤ 2.19. S1 and S2 are determined according to ASTM D4895 standard. By defining the standard specific gravity range of the first and second binders, it is ensured that the first and second binders have suitable molecular chain flexibility and density. In conjunction with the defined content range of the first and second binders and the relationship formula, a stable bonding network is formed, further improving the overall flexibility and mechanical strength of the positive electrode sheet, ensuring good processing performance of the positive electrode sheet, avoiding the obstruction of ion conduction due to excessively dense molecular chains, and adapting to the fibrillation process in dry preparation, indirectly optimizing processing efficiency.
[0033] Specifically, the standard specific gravity of the first adhesive and the second adhesive includes, but is not limited to, any one value or a range of any two values from 2.12, 2.13, 2.14, 2.15, 2.16, 2.17, 2.18, and 2.19. The standard specific gravity of the first adhesive and the second adhesive may be the same or different.
[0034] In some embodiments, the first adhesive includes at least one of polytetrafluoroethylene and polytetrafluoroethylene derivatives; The second adhesive includes at least one of polytetrafluoroethylene and polytetrafluoroethylene derivatives.
[0035] The first and second binders are made of polytetrafluoroethylene (PTFE) binders, which are suitable for the solvent-free characteristics of the dry preparation process. At the same time, their excellent high temperature resistance, electrolyte corrosion resistance, and high bonding strength are utilized to further improve the mechanical stability and safety of the positive electrode sheet and improve the cycle life of the battery.
[0036] Polytetrafluoroethylene derivatives can be selected from perfluoroethylene propylene (FEP), polyvinylidene fluoride-tetrafluoroethylene copolymer (PVDF-TFE), etc. The first and second binders can be the same or different. It should be noted that the positive electrode sheet can also be used in combination with other binders and polytetrafluoroethylene binders to further improve the bonding strength and safety performance.
[0037] In some embodiments, the thickness of the first positive electrode material layer 2 is 10-150 μm, and the thickness of the second positive electrode material layer 3 is 10-150 μm. By limiting the thickness range of the first positive electrode material layer 2 and the second positive electrode material layer 3, the energy density, mechanical properties, and ion conductivity of the positive electrode sheet can be controlled within a suitable range, thereby further improving the energy density and rate performance of the battery.
[0038] Specifically, the thickness of the first positive electrode material layer 2 and the second positive electrode material layer 3 includes, but is not limited to, any one value or a range of any two values among 10μm, 30μm, 50μm, 70μm, 90μm, 110μm, 130μm, and 150μm.
[0039] In some embodiments, the first active material includes at least one of monocrystalline particles and polycrystalline particles, and the second active material includes at least one of monocrystalline particles and polycrystalline particles. The combined use of monocrystalline and polycrystalline particles further improves the energy density of the battery.
[0040] In some embodiments, the first positive electrode material layer 2 further includes a first conductive agent, and the second positive electrode material layer 3 further includes a second conductive agent; The first conductive agent includes at least one of Ketjen black, graphite, hard carbon, soft carbon, carbon nanotubes, graphene, porous carbon, superconducting carbon black, acetylene black, furnace black, and whisker carbon nanotubes. The second conductive agent includes at least one of Ketjen black, graphite, hard carbon, soft carbon, carbon nanotubes, graphene, porous carbon, superconducting carbon black, acetylene black, furnace black, and whisker carbon nanotubes. By adding the first and second conductive agents, a continuous electron conduction network is constructed in the positive electrode, improving the electron conduction efficiency of the electrode. The types of conductive agents in the first positive electrode material layer 2 and the second positive electrode material layer 3 can be the same or different. For example, graphite can be used in the first positive electrode material layer 2 and carbon nanotubes can be used in the second positive electrode material layer 3. This ensures both electron conduction efficiency and uniform dispersion of the outer conductive agent, avoiding performance inconsistencies caused by agglomeration, while also helping to improve interlayer bonding strength.
[0041] Furthermore, different types of conductive agents can be combined and used, such as Ketjenblack and carbon nanotubes, carbon nanotubes and graphene, and carbon nanotubes, graphene and porous carbon, to improve electron conduction efficiency and dispersion through synergistic effects.
[0042] In some embodiments, the first active material and the second active material are each independently selected from at least one of lithium nickel cobalt manganese oxide, lithium iron manganese phosphate, lithium iron phosphate, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium-rich manganese-based oxide, lithium nickel manganese oxide, lithium vanadium phosphate, and lithium vanadium oxide phosphate. By using the above-mentioned active materials in combination, the safety performance and energy density of the battery can be further improved.
[0043] In some embodiments, the mass content of the first active material in the first positive electrode material layer 2 is 50%-99%, and the content of the first conductive agent is 0.1%-5%.
[0044] The second active material in the second positive electrode material layer 3 has a mass content of 50%-99% and a content of 0.1%-5%.
[0045] In a preferred embodiment, the mass content of the first active material in the first positive electrode material layer 2 is 70%-99%, and the mass content of the second active material in the second positive electrode material layer 3 is 70%-99%.
[0046] In some embodiments, the current collector 1 includes one of pure aluminum current collector 1, porous current collector 1, composite current collector 1, and carbon-coated current collector 1. A suitable current collector 1 can be selected according to different performance requirements, thereby improving the bonding strength between the first positive electrode active material layer and the current collector 1 and reducing interlayer delamination.
[0047] One embodiment of this application provides a method for preparing the positive electrode sheet as described above, comprising the following steps: The first active material and the first conductive agent are mixed, and then the first binder is added and dispersed. Then, the mixture is heated to undergo fibrillation treatment to obtain the first mixture. The first mixture is then calendered into a film to obtain the first positive electrode film.
[0048] The second active material and the second conductive agent are mixed, and then the second binder is added and dispersed. Then, the mixture is heated to undergo fibrillation treatment to obtain the second mixture. The second mixture is then calendered into a film to obtain the second positive electrode film.
[0049] The first and second positive electrode films are stacked and subjected to multiple calendering processes to obtain a composite film.
[0050] The composite membrane is hot-pressed with current collector 1 to obtain the positive electrode.
[0051] Compared with existing processes, the above preparation method does not require kneading and mixing. The mixture can be directly processed into a film after fibrillation, which improves production efficiency.
[0052] Specifically, the fibrillation treatment apparatus includes, but is not limited to, at least one of a high-speed planetary mixer, an air jet mill, and a screw extruder, with a fibrillation treatment time of 0.1-24 h and a fibrillation treatment temperature of 40-200 °C, preferably 60-150 °C.
[0053] The calendering temperature is 25-200℃. Preferably, the calendering temperature is 60-150℃. Specifically, the calendering equipment can be a pair of heated rollers or a multi-stage roller system.
[0054] The temperature for hot-pressing the composite membrane with the current collector 1 is 40-200℃, preferably 60-150℃.
[0055] In one embodiment, the mixing temperature of the first active material, the first conductive agent, and the first binder is 0-40°C, preferably 10-35°C; the mixing time is 0.1-24 hours, preferably 0.1-5 hours.
[0056] In a preferred embodiment, the fibrillation treatment temperature is 60-150°C and the treatment time is 0.1-5 hours.
[0057] In a preferred embodiment, the calendering temperature is 60-150°C. The temperature at which the first positive electrode material layer 2 and the current collector 1 are hot-pressed is 40-200°C, preferably 60-150°C.
[0058] One embodiment of this application provides a battery including a positive electrode sheet as described above, or a positive electrode sheet prepared by the above-described preparation method. By selecting the above-described positive electrode sheet, the energy density of the battery is improved, and the cycle stability of the battery is enhanced. It should be noted that the battery can be a stacked or wound battery. Specifically, the battery can be a liquid battery, a semi-solid battery, or a solid battery.
[0059] The battery also includes a negative electrode, a separator, and an electrolyte.
[0060] In some embodiments, the negative electrode includes at least one of graphite negative electrode, silicon-carbon negative electrode, lithium metal negative electrode, and alloy negative electrode.
[0061] In some embodiments, the electrolyte includes a liquid electrolyte, a semi-solid electrolyte, and an all-solid electrolyte, wherein the semi-solid electrolyte is obtained by mixing liquid electrolyte and solid electrolyte in any proportion.
[0062] Liquid electrolytes include conventional electrolytes, gel electrolytes, in-situ polymerized electrolytes, eutectic electrolytes, or ionic liquid electrolytes. Conventional electrolytes include organic solvents, lithium salts, and additives. Solvents include, but are not limited to, PC (propylene carbonate), EC (ethylene carbonate), DMC (dimethyl carbonate), EMC (ethyl methyl carbonate), DEC (diethyl carbonate), and DME (ethylene glycol dimethyl ether). Gel electrolytes include a polymer matrix, plasticizing solvents, and lithium salts. In-situ polymerized electrolytes include polymer monomers, lithium salts, solvents, and initiators. Eutectic electrolytes include a small-molecule polar matrix and lithium salts. Ionic liquid electrolytes include ionic liquids and lithium salts. Lithium salts include, but are not limited to, lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate (LiAsF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroantimonyate (LiSbF6), lithium bis(trifluoromethanesulfonate imide) (LiTFSI or LiN(SO2CF2)2), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(fluorosulfonyl)imide (LiFSI or LiN(SO2CF3)2), lithium perchlorate (LiClO4), lithium iodide (LiI), and lithium magnesium bis(fluorosulfonyl)imide (Li2Mg(N(SO2CF3)2)2).
[0063] Solid electrolytes include, but are not limited to, at least one of the following: NASICON (sodium fast ion conductor) type solid electrolyte, LISICON (lithium fast ion conductor) type solid electrolyte, garnet type solid electrolyte, perovskite type solid electrolyte, anti-perovskite type solid electrolyte, sulfide solid electrolyte, halide solid electrolyte, and polymer electrolyte.
[0064] Polymer electrolytes include polymers and lithium salts; polymers include, but are not limited to, PEO (polyethylene oxide), PVDF (polyvinylidene fluoride), PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene), PMMA (polymethyl methacrylate), and PAN (polyacrylonitrile); lithium salts include, but are not limited to, LiPF6, LiTFSI, LiFSI, and LiDFOB.
[0065] Liquid electrolytes are used in at least one of pouch cells, cylindrical cells, or prismatic cells; semi-solid electrolytes are used in at least one of pouch cells, cylindrical cells, or prismatic cells; and all-solid electrolytes are used in at least one of pouch cells, cylindrical cells, or prismatic cells.
[0066] In some embodiments, the diaphragm is selected from materials such as polypropylene (PP), polyethylene (PE), and their composite membranes. Further, at least one side of the diaphragm is provided with a coating, which includes at least one of: an oxide solid electrolyte, an alkaline oxide, and a polymer. The oxide solid electrolyte includes at least one of: NASICON (sodium fast ion conductor) type solid electrolyte, garnet type solid electrolyte, and perovskite type solid electrolyte. The alkaline oxide includes at least one of: alumina, silicon oxide, zirconium oxide, titanium oxide, and boehmite. The polymer includes at least one of: polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polymethyl methacrylate (PMMA), and aramid fiber.
[0067] One embodiment of this application provides an electrical device including the battery described above. By using the battery described above, which has high energy density and good cycle stability, the battery life of the electrical device is improved. Exemplary examples include, but are not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, aircraft, and robots.
[0068] The present application will be further illustrated by the following examples.
[0069] Example 1 This embodiment illustrates the positive electrode sheet and battery disclosed in this application, and includes the following operation steps: 1. Preparation of positive electrode sheet (1) First positive electrode film: The first active material is polycrystalline LiNi with a D50 of 10 μm. 0.8 Co 0.1 Mn 0.1O The first active material, conductive carbon black, and the first binder PTFE were added to a high-speed mixer in a mass ratio of 96:2:2. After thorough mixing, the mixture was subjected to high-speed fiberization at 90°C to obtain a fiberized mixture. This mixture was then calendered at 100°C using a two-roll mill to form a first positive electrode film with a thickness of 250 μm. The standard specific gravity of the first binder was 2.14 g / cm³. 3 .
[0070] (2) Second positive electrode film: The second active material is polycrystalline LiNi with a D50 of 5μm. 0.8 Co 0.1 Mn 0.1OThe first active material, conductive carbon black, and the second binder PTFE were added to a high-speed mixer in a mass ratio of 96:2:2 for mixing and fiberization to obtain a fiberized mixture. This mixture was then calendered at 100°C using a two-roll mill to form a second positive electrode film with a thickness of 250 μm. The standard specific gravity of the second binder was 2.14 g / cm³. 3 .
[0071] (3) Composite film: The first positive electrode film and the second positive electrode film are stacked together in sequence and rolled multiple times at 90°C using an open mill to reduce the thickness of the double-layer positive electrode film to 80μm; (4) Current collector composite: The thinned composite film is bonded to the carbon-coated current collector, bringing the first positive electrode film into contact with the carbon-coated current collector; the carbon coating layer of the current collector is softened by hot pressing at 100°C using a two-roll mill, and the first positive electrode film and the carbon-coated current collector are bonded together to obtain the positive electrode sheet. The areal density of the positive electrode sheet is maintained at 25 mg / cm³. 2 The cross-sectional SEM morphology of the positive electrode is as follows: Figure 1 As shown.
[0072] 2. Negative electrode plate The negative electrode is a lithium metal negative electrode.
[0073] 3. Preparation of electrolyte Ethylene carbonate and dimethyl carbonate were mixed in a mass ratio of 1:1, dispersed, and then lithium salt LiFSI was added with a concentration of 1 mol / L.
[0074] 4. Battery manufacturing A separator is placed between the positive and negative electrode sheets prepared above. Then, the sandwich structure consisting of the positive electrode sheet, negative electrode sheet and separator is stacked, packaged with aluminum-plastic film, and the battery is obtained after liquid injection and formation.
[0075] Examples 2-21, Comparative Examples 1-6 Examples 2-21 and Comparative Examples 1-6 are used to illustrate the positive electrode sheet and battery disclosed in this application, including most of the operating steps in Example 1 above, except that the formulation in Table 1 is used.
[0076] Comparative Example 7 Comparative Example 7 is used to illustrate the positive electrode sheet and battery disclosed in this application, including most of the operating steps in Example 1, except that a first positive electrode material layer is not provided.
[0077] Comparative Example 8 Comparative Example 8 is used to illustrate the positive electrode sheet and battery disclosed in this application, including most of the operating steps in Example 1, except that a second positive electrode material layer is not provided.
[0078] Table 1 Performance Test I. The following performance tests were conducted on the positive electrode sheets and batteries prepared in the above-mentioned examples and comparative examples: 1. Mechanical strength test of the positive electrode sheet: The mechanical strength test method of the dry electrode film was carried out in accordance with the standard ASTM D638. The test film size was type IV, and the test speed was 50 mm / min. Five groups of data were tested for each sample, and the tensile strength was calculated by dividing the maximum load (Newton) by the minimum cross-sectional area.
[0079] 2. Cycle test: Charge to 4.3 V at 0.33 C at 25 °C; discharge at 1 C; discharge to 2.8 V, record the specific capacity of the first discharge, with the unit of mAh / g, and then cycle 100 times to record the capacity retention rate.
[0080] 3. Energy density: Weigh the battery at 25 °C by a balance, then charge it at a constant current of 0.1 C to 4.3 V, charge it at a constant voltage to 0.05 C, and then discharge it at a constant current of 0.1 C to 2.8 V. Record the discharge energy of the battery. The energy density of the battery can be calculated by dividing the discharge energy of the battery by the weight of the battery.
[0081] 4. Rate performance test: The cells prepared in the examples and comparative examples were charged and discharged at a constant current for 3 cycles at the rates of 0.1 C, 0.5 C, 1 C, 2 C, and 5 C. The charge-discharge voltage range was 2.8 - 4.3 V, and the capacity retention rate at the 2 C rate was recorded.
[0082] The test results are shown in Table 2.
[0083] Table 2 Figure 2 It is the cross-sectional SEM image of Example 1. The first positive electrode material layer and the second positive electrode material layer can be observed, and the binder can be observed as fibrous filaments.
[0084] From the test results of the examples and comparative examples in Table 2, it can be seen that when the conditions of the formula 1.5 ≤ (C1 D (2.2 - S1) / (C2 d (2.2 - S2) ≤ 5 and the mass content ranges of the first binder and the second binder are satisfied, the battery has good cycle stability and high energy density. And when 0.1 < d / D < 0.8, the battery also has good rate performance.
[0085] Furthermore, when the particle sizes of the first and second active materials satisfy 5≤D≤20 and 0.1≤d≤10, and the standard specific gravity ranges of the first and second binders satisfy 2.12≤S1≤2.19 and 2.12≤S2≤2.19, the positive electrode sheet possesses higher mechanical strength while also exhibiting better cycle stability, higher energy density, and better rate performance, achieving good processing performance while ensuring good electrochemical performance.
[0086] The terms “first,” “second,” etc., in this application (if applicable) are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.
[0087] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A positive electrode plate, characterized in that, The device includes a current collector, a first positive electrode material layer, and a second positive electrode material layer. The first positive electrode material layer is disposed on at least one side of the current collector, and the second positive electrode material layer is disposed on the side of the first positive electrode material layer opposite to the current collector. The first positive electrode material layer includes a first active material and a first binder, and the second positive electrode layer includes a second active material and a second binder. The positive electrode plate satisfies the following relationship: 1.5≤(C1 D (2.2-S1) / (C2 d (2.2-S2)≤5, Wherein, the mass content of the first binder in the first positive electrode material layer is C1%, and the mass content of the second binder in the second positive electrode material layer is C2%; 1%≤C1%≤5%, 2%≤C2%≤10%; The D50 of the first active substance is Dμm, and the D50 of the second active substance is dμm; The standard specific gravity of the first adhesive is S1, and the standard specific gravity of the second adhesive is S2.
2. The positive electrode sheet according to claim 1, characterized in that, In the positive electrode, 0.1 <d / D<0.8。 3. The positive electrode sheet according to claim 1 or 2, characterized in that, 5≤D≤20, 0.1≤d≤10.
4. The positive electrode sheet according to claim 1, characterized in that, 2.12≤S1≤2.19, 2.12≤S2≤2.
19.
5. The positive electrode sheet according to claim 1, characterized in that, The first adhesive includes at least one of polytetrafluoroethylene and polytetrafluoroethylene derivatives; The second adhesive includes at least one of polytetrafluoroethylene and polytetrafluoroethylene derivatives.
6. The positive electrode sheet according to claim 1, characterized in that, The thickness of the first positive electrode material layer is 10-150 μm, and the thickness of the second positive electrode material layer is 10-150 μm.
7. The positive electrode sheet according to claim 1, characterized in that, The first active material includes at least one of monocrystalline particles and polycrystalline particles, and the second active material includes at least one of monocrystalline particles and polycrystalline particles.
8. The positive electrode sheet according to claim 1, characterized in that, The first positive electrode material layer further includes a first conductive agent, and the second positive electrode material layer further includes a second conductive agent; The first conductive agent includes at least one of Ketjen black, graphite, hard carbon, soft carbon, carbon nanotubes, graphene, porous carbon, superconducting carbon black, acetylene black, furnace black, and whisker carbon nanotubes. The second conductive agent includes at least one of Ketjen black, graphite, hard carbon, soft carbon, carbon nanotubes, graphene, porous carbon, superconducting carbon black, acetylene black, furnace black, and whisker carbon nanotubes.
9. A battery, characterized in that, Including the positive electrode sheet as described in any one of claims 1-8.
10. An electrical appliance, characterized in that, Includes the battery as described in claim 9.