Positive pole piece of lithium ion battery as well as preparation and application of positive pole piece

Abstract

The embodiment of the invention relates to a lithium ion battery positive pole piece as well as preparation and application thereof. The lithium ion battery positive pole piece sequentially comprises an aluminum foil, a carbon layer, an active substance layer and a solid electrolyte layer, wherein the carbon layer comprises a porous carbon source and a first binder, the aperture of the porous carbon source is 2nm-100nm, and the porosity is 30%-85%; the active material layer comprises a positive active material, a conductive agent and a second binder; the solid electrolyte layer comprises a solid electrolyte and a third binder; and the carbon layer is used for increasing the contact area between the electrolyte and the active substance layer, so that the electrolyte can infiltrate the active substance layer, a smooth transmission path is provided for lithium ions, the interface resistance caused by non-uniform infiltration is reduced, and the cycle performance of the battery is improved. When the lithium ion battery positive pole piece provided by the invention is applied to a lithium ion battery, the battery can have good cycle performance.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and particularly relates to a positive electrode sheet of a lithium-ion battery, its preparation and application. Background Art

[0002] With the vigorous development of China's new energy industry, lithium-ion batteries have become the first choice for battery systems in various energy storage fields due to their advantages of high energy density. However, during the production and use of lithium-ion batteries, the uneven infiltration of the electrolyte into the electrode sheet has an adverse effect on the performance of the battery, restricting the development of lithium-ion batteries.

[0003] On the one hand, the uneven infiltration of the electrolyte into the electrode sheet will cause the lithium-ion transmission path in the active material to become longer, hindering the shuttling of lithium ions between the positive and negative electrodes; on the other hand, the uneven infiltration of the electrolyte into the electrode sheet makes the active material that has not contacted the electrolyte unable to participate in the electrochemical reaction of the battery. This leads to an increase in the interfacial resistance of the battery, thereby affecting the cycle performance of the battery.

[0004] Based on this, how to improve the wettability of the electrolyte on the electrode has become an urgent technical problem to be solved. Summary of the Invention

[0005] The purpose of the present invention is to provide a positive electrode sheet of a lithium-ion battery, its preparation and application. By coating a carbon layer prepared from a porous carbon source on an aluminum foil, the contact area between the electrolyte and the electrode sheet is increased, thereby improving the wettability of the electrolyte on the electrode sheet. The positive electrode sheet of the lithium-ion battery provided by the present invention can be applied to a lithium-ion battery, enabling the battery to have good cycle life.

[0006] To this end, in the first aspect, the present invention provides a positive electrode sheet of a lithium-ion battery. The positive electrode sheet of the lithium-ion battery sequentially includes an aluminum foil, a carbon layer, an active material layer, and a solid electrolyte layer; wherein, the carbon layer includes a porous carbon source and a first binder, the pore diameter of the porous carbon source is 2 nm - 100 nm, and the porosity is 30% - 85%; the active material layer includes a positive electrode active material, a conductive agent, and a second binder; the solid electrolyte layer includes a solid electrolyte and a third binder;

[0007] The carbon layer is used to increase the contact area between the electrolyte and the active material layer, enabling the electrolyte to uniformly infiltrate the active material layer, providing a smooth transmission path for lithium ions, reducing the interfacial resistance caused by uneven infiltration, and improving the cycle performance of the battery.

[0008] Preferably, the percentage of the mass of the first binder in the mass of the carbon layer is 1% - 20%, and the percentage of the mass of the porous carbon source in the mass of the carbon layer is 80% - 99%;

[0009] The percentage of the mass of the second binder in the mass of the active material layer is 1%-6%, the percentage of the mass of the positive electrode active material in the mass of the active material layer is 85%-96%, and the percentage of the mass of the conductive agent in the mass of the active material layer is 1%-10%;

[0010] The percentage of the mass of the third binder in the mass of the solid electrolyte layer is 2%-15%, and the percentage of the mass of the solid electrolyte in the mass of the solid electrolyte layer is 85%-98%.

[0011] Preferably, the thickness of the carbon layer is 0.1μm - 20μm;

[0012] The thickness of the active material layer is 10μm - 150μm;

[0013] The thickness of the solid electrolyte layer is 0.1μm - 30μm.

[0014] Preferably, the porous carbon source includes one or more of activated carbon, activated carbon fiber, carbon molecular sieve, graphene, acetylene black, and carbon nanotube;

[0015] The positive electrode active material includes one or more of lithium cobaltate, lithium manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium titanate, and nickel cobalt manganese ternary material;

[0016] The conductive agent includes one or more of graphite, carbon black, activated carbon, activated carbon fiber, carbon molecular sieve, graphene, acetylene black, and carbon nanotube;

[0017] The solid electrolyte includes one or more of perovskite-type solid electrolyte, NASICON-type solid electrolyte, LISICON-type solid electrolyte, and garnet-type solid electrolyte;

[0018] The first binder includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, polyolefins, polyvinyl alcohol, polyacrylic acid, and polyurethane;

[0019] The second binder includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, polyolefins, polyvinyl alcohol, polyacrylic acid, and polyurethane;

[0020] The third binder includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, polyolefins, polyvinyl alcohol, polyacrylic acid, and polyurethane.

[0021] In a second aspect, the present invention provides a method for preparing the positive electrode tab of the lithium-ion battery according to the first aspect above, and the preparation method includes:

[0022] Add a porous carbon source, a first binder, and a first solvent to a stirring device. After stirring evenly, a carbon layer slurry with a solid content of 30%-70% is obtained. Coat the carbon layer slurry on one side of the aluminum foil, and place the coated aluminum foil in a drying device and bake it at 80°C - 170°C for 3 min - 30 min to obtain a carbon layer; wherein, the pore size of the porous carbon source is 2 nm - 100 nm, and the porosity is 30% - 85%;

[0023] Add a positive electrode active material, a conductive agent, a second binder, and a second solvent to a stirring device. After stirring evenly, a positive electrode active material slurry with a solid content of 45%-75% is obtained. Coat the positive electrode active material slurry on the carbon layer, and bake it in a drying device at 80°C - 170°C for 3 min - 30 min to obtain an active material layer;

[0024] Add a solid electrolyte, a third binder, and a third solvent to a stirring device. After stirring evenly, a solid electrolyte slurry with a solid content of 30%-70% is obtained. Coat the solid electrolyte slurry on the active material layer, and bake it in a drying device at 80°C - 170°C for 3 min - 30 min to obtain a solid electrolyte layer, and finally obtain the required positive electrode plate of the lithium-ion battery.

[0025] Preferably, the percentage of the mass of the first binder in the mass of the carbon layer is 1% - 20%, and the percentage of the mass of the carbon source in the mass of the carbon layer is 80% - 99%;

[0026] The percentage of the mass of the second binder in the mass of the active material layer is 1% - 6%, the percentage of the mass of the positive electrode active material in the mass of the active material layer is 85% - 96%, and the percentage of the mass of the conductive agent in the mass of the active material layer is 1% - 10%;

[0027] The percentage of the mass of the third binder in the mass of the solid electrolyte layer is 2% - 15%, and the percentage of the mass of the solid electrolyte in the mass of the solid electrolyte layer is 85% - 98%.

[0028] Preferably, the porous carbon source includes one or more of activated carbon, activated carbon fiber, carbon molecular sieve, graphene, carbon nanotube;

[0029] The positive electrode active material includes one or more of lithium cobaltate, lithium manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium titanate, nickel cobalt manganese ternary material;

[0030] The conductive agent includes one or more of graphite, carbon black, activated carbon, activated carbon fiber, carbon molecular sieve, graphene, acetylene black, carbon nanotube;

[0031] The solid electrolyte includes one or more of perovskite-type solid electrolytes, NASICON-type solid electrolytes, LISICON-type solid electrolytes, and garnet-type solid electrolytes;

[0032] The first binder includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, polyolefins, polyvinyl alcohol, polyacrylic acid, and polyurethane;

[0033] The second binder includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, polyolefins, polyvinyl alcohol, polyacrylic acid, and polyurethane;

[0034] The third binder includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, polyolefins, polyvinyl alcohol, polyacrylic acid, and polyurethane;

[0035] The first solvent includes one or more of N-methylpyrrolidone, dimethyl carbonate, methanol, ethanol, propanol, butanol, and isopropanol;

[0036] The second solvent includes one or more of N-methylpyrrolidone, dimethyl carbonate, methanol, ethanol, propanol, butanol, and isopropanol;

[0037] The third solvent includes one or more of N-methylpyrrolidone, dimethyl carbonate, methanol, ethanol, propanol, butanol, and isopropanol.

[0038] Preferably, when preparing the carbon layer slurry, the revolution speed of the stirring equipment is 20 rpm - 35 rpm, the rotation speed is 200 rpm - 3000 rpm, and the stirring time is 30 min - 150 min;

[0039] When preparing the positive electrode active material slurry, the revolution speed of the stirring equipment is 20 rpm - 35 rpm, the rotation speed is 200 rpm - 3000 rpm, and the stirring time is 30 min - 150 min;

[0040] When preparing the solid electrolyte slurry, the revolution speed of the stirring equipment is 20 rpm - 35 rpm, the rotation speed is 200 rpm - 3000 rpm, and the stirring time is 30 min - 150 min.

[0041] Preferably, the thickness of the carbon layer is 0.1 μm - 20 μm;

[0042] The thickness of the active material layer is 10 μm - 150 μm;

[0043] The thickness of the solid electrolyte layer is 0.1 μm - 30 μm.

[0044] In a third aspect, the present invention provides a lithium-ion battery, which includes the positive electrode sheet of the lithium-ion battery described in the first aspect above or the positive electrode sheet of the lithium-ion battery prepared by the preparation method described in the second aspect above.

[0045] For the positive electrode sheet of the lithium-ion battery provided by the present invention, a carbon layer prepared from a porous carbon source is coated on an aluminum foil to increase the contact area between the electrolyte and the active material layer, enabling the electrolyte to uniformly infiltrate the active material layer, providing a smooth transmission path for lithium ions, reducing the interfacial resistance caused by uneven infiltration, and improving the cycling performance of the battery. When the positive electrode sheet of the lithium-ion battery provided by the present invention is applied in a lithium-ion battery, the battery can have good cycling performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is a schematic structural diagram of the positive electrode sheet of the lithium-ion battery provided by an embodiment of the present invention;

[0047] Figure 2 is a flowchart of the preparation method of the positive electrode sheet of the lithium-ion battery provided by an embodiment of the present invention;

[0048] Figure 3 is a comparative diagram of cycling curves measured for coin cells assembled with the positive electrode sheets prepared in Example 1, Example 3, and Comparative Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0049] The technical solutions of the present invention will be further described in detail below with reference to the drawings and embodiments.

[0050] The present invention provides a positive electrode sheet for a lithium-ion battery, as Figure 1 shown, the positive electrode sheet for the lithium-ion battery sequentially includes an aluminum foil, a carbon layer, an active material layer, and a solid electrolyte layer; wherein, the carbon layer includes a porous carbon source and a first binder, the pore diameter of the porous carbon source is 2 nm - 100 nm, and the porosity is 30% - 85%; the active material layer includes a positive electrode active material, a conductive agent, and a second binder; the solid electrolyte layer includes a solid electrolyte and a third binder;

[0051] The carbon layer is used to increase the contact area between the electrolyte and the active material layer, enabling the electrolyte to uniformly infiltrate the active material layer, providing a smooth transmission path for lithium ions, reducing the interfacial resistance caused by uneven infiltration, and improving the cycling performance of the battery.

[0052] Among them, the mass percentage of the first binder in the carbon layer is 1%-20%, and the mass percentage of the porous carbon source in the carbon layer is 80%-99%; the mass percentage of the second binder in the active material layer is 1%-6%, the mass percentage of the positive electrode active material in the active material layer is 85%-96%, and the mass percentage of the conductive agent in the active material layer is 1%-10%; the mass percentage of the third binder in the solid electrolyte layer is 2%-15%, and the mass percentage of the solid electrolyte in the solid electrolyte layer is 85%-98%.

[0053] The thickness of the carbon layer is 0.1 μm - 20 μm; the thickness of the active material layer is 10 μm - 150 μm; the thickness of the solid electrolyte layer is 0.1 μm - 30 μm.

[0054] The porous carbon source includes one or more of activated carbon, activated carbon fiber, carbon molecular sieve, graphene, acetylene black, and carbon nanotube; the positive electrode active material includes one or more of lithium cobaltate, lithium manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium titanate, and nickel cobalt manganese ternary material; the conductive agent includes one or more of graphite, carbon black, activated carbon, activated carbon fiber, carbon molecular sieve, graphene, acetylene black, and carbon nanotube; the solid electrolyte includes one or more of perovskite-type solid electrolyte, NASICON-type solid electrolyte, LISICON-type solid electrolyte, and garnet-type solid electrolyte.

[0055] The first binder includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, polyolefins, polyvinyl alcohol, polyacrylic acid, and polyurethane; the second binder includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, polyolefins, polyvinyl alcohol, polyacrylic acid, and polyurethane; the third binder includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, polyolefins, polyvinyl alcohol, polyacrylic acid, and polyurethane.

[0056] The present invention also provides a preparation method of the above-mentioned lithium ion positive electrode sheet. The steps of the preparation method are as Figure 2 shown and include the following steps:

[0057] Step 110: Add the porous carbon source, the first binder, and the first solvent into a stirring device. After stirring evenly, a carbon layer slurry with a solid content of 30%-70% is obtained. Coat the carbon layer slurry on one side of the aluminum foil, and place the coated aluminum foil in a drying device and bake it at 80°C - 170°C for 3 min - 30 min to obtain a carbon layer;

[0058] In this step, the pore size of the porous carbon source is 2 nm - 100 nm, and the porosity is 30% - 85%. The porous carbon source includes one or more of activated carbon, activated carbon fiber, carbon molecular sieve, graphene, acetylene black, and carbon nanotube; the first binder includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, polyolefin, polyvinyl alcohol, polyacrylic acid, and polyurethane; the first solvent includes one or more of N-methylpyrrolidone, dimethyl carbonate, methanol, ethanol, propanol, butanol, and isopropanol.

[0059] The stirring equipment used in the present invention includes a double planetary mixer, a ball mill disperser, a screw mixer, a VC high-efficiency mixer, a magnetic vertical stirring tank, or a high-speed mixer; when the stirring equipment performs stirring, the revolution speed is 20 rpm - 35 rpm, the rotation speed is 200 rpm - 3000 rpm, and the stirring time is 30 min - 150 min. The drying equipment used in the present invention includes a vacuum drying oven, a forced-air drying oven, a hot air circulation oven, or a tunnel kiln.

[0060] The thickness of the prepared carbon layer is 0.1 μm - 20 μm. In the prepared carbon layer, the mass percentage of the first binder in the carbon layer is 1% - 20%, and the mass percentage of the porous carbon source in the carbon layer is 80% - 99%.

[0061] Step 120: Add the positive electrode active material, the conductive agent, the second binder, and the second solvent to the stirring equipment. After stirring evenly, a positive electrode active material slurry with a solid content of 45% - 75% is obtained. Coat the positive electrode active material slurry on the carbon layer and bake it in the drying equipment at 80°C - 170°C for 3 min - 30 min to obtain an active material layer.

[0062] In this step, the positive electrode active material includes one or more of lithium cobaltate, lithium manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium titanate, and nickel cobalt manganese ternary materials; the conductive agent includes one or more of graphite, carbon black, activated carbon, activated carbon fiber, carbon molecular sieve, graphene, acetylene black, and carbon nanotube; the second binder includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, polyolefin, polyvinyl alcohol, polyacrylic acid, and polyurethane; the second solvent includes one or more of N-methylpyrrolidone, dimethyl carbonate, methanol, ethanol, propanol, butanol, and isopropanol.

[0063] The stirring equipment used in this step also includes a double planetary mixer, a ball mill disperser, a screw mixer, a VC high-efficiency mixer, a magnetic vertical stirring tank, or a high-speed mixer; when the stirring equipment performs stirring, the revolution speed is 20 rpm - 35 rpm, the rotation speed is 200 rpm - 3000 rpm, and the stirring time is 30 min - 150 min. The drying equipment used in this step also includes a vacuum drying oven, a forced-air drying oven, a hot air circulation oven, or a tunnel kiln.

[0064] The thickness of the prepared active material layer is 10 μm - 150 μm. In the prepared active material layer, the mass percentage of the second binder in the active material layer is 1% - 6%, the mass percentage of the positive electrode active material in the active material layer is 85% - 96%, and the mass percentage of the conductive agent in the active material layer is 1% - 10%.

[0065] Step 130: Add the solid electrolyte, the third binder, and the third solvent into a stirring device. After stirring evenly, a solid electrolyte slurry with a solid content of 30% - 70% is obtained. Coat the solid electrolyte slurry on the active material layer and bake it in a drying device at 80°C - 170°C for 3 min - 30 min to obtain a solid electrolyte layer, and finally obtain the desired positive electrode sheet of the lithium-ion battery.

[0066] In this step, the solid electrolyte includes one or more of perovskite-type solid electrolytes, NASICON-type solid electrolytes, LISICON-type solid electrolytes, and garnet-type solid electrolytes; the third binder includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, polyolefins, polyvinyl alcohol, polyacrylic acid, and polyurethane; the third solvent includes one or more of N-methylpyrrolidone, dimethyl carbonate, methanol, ethanol, propanol, butanol, and isopropanol.

[0067] The stirring device used in this step also includes a double planetary mixer, a ball mill disperser, a screw mixer, a VC high-efficiency mixer, a magnetic vertical stirring tank, or a high-speed mixer; when the stirring device stirs, the revolution speed is 20 rpm - 35 rpm, the rotation speed is 200 rpm - 3000 rpm, and the stirring time is 30 min - 150 min. The drying device used in this step also includes a vacuum drying oven, a forced-air drying oven, a hot air circulation oven, or a tunnel kiln.

[0068] The thickness of the prepared solid electrolyte layer is 0.1 μm - 30 μm. In the prepared solid electrolyte layer, the mass percentage of the third binder in the solid electrolyte layer is 2% - 15%, and the mass percentage of the solid electrolyte in the solid electrolyte layer is 85% - 98%.

[0069] For the positive electrode sheet of the lithium-ion battery provided by the present invention, by coating a carbon layer prepared from a porous carbon source on the aluminum foil, the contact area between the electrolyte and the active material layer is improved, so that the electrolyte can uniformly infiltrate the active material layer, provide a smooth transmission path for lithium ions, reduce the interfacial resistance caused by uneven infiltration, and improve the cycle performance of the battery. When the positive electrode sheet of the lithium-ion battery provided by the present invention is applied in a lithium-ion battery, the battery can have good cycle performance.

[0070] The positive electrode plate of the lithium-ion battery prepared by the present invention includes an aluminum foil and multiple coating layers. Specifically, they are, in sequence, the aluminum foil, the carbon layer, the active material layer, and the solid electrolyte layer. When applied in a lithium-ion battery, it can endow the battery with good cycling performance and safety performance.

[0071] To more clearly illustrate the purpose and advantages of the present invention, the following further elaborates on the present invention in combination with embodiments. In addition, the embodiments described in the present invention are only partial embodiments. All other embodiments obtained by those skilled in the art without creative efforts based on the embodiments described in the present invention fall within the protection scope of the present invention. Additionally, it should be understood that these embodiments are only for more detailed description and should not be construed as limiting the present invention in any form, that is, it is not intended to limit the protection scope of the present invention.

[0072] First, introduce the embodiments provided by the present invention.

[0073] Example 1

[0074] Step 1: Add carbon nanotubes with a pore size of 20 nm and a porosity of 85%, polytetrafluoroethylene, and N-methylpyrrolidone to a double planetary mixer, and adjust the revolution speed of the stirring to 30 rpm, the rotation speed to 2800 rpm, and the stirring time to 60 min. After stirring evenly, a carbon layer slurry with a solid content of 45% is obtained, and then it is coated on one side of the aluminum foil and subsequently placed in a vacuum drying oven and baked at 120 °C for 10 min to obtain a carbon layer with a thickness of 6 μm; wherein, the mass percentage of polytetrafluoroethylene in the carbon layer is 10%, and the mass percentage of carbon nanotubes in the carbon layer is 90%;

[0075] Step 2: Add lithium cobaltate, carbon black, polyvinylidene fluoride, and N-methylpyrrolidone to a double planetary mixer with a revolution speed of 30 rpm, a rotation speed of 1800 rpm, and a stirring time of 60 min. After stirring evenly, a positive electrode active material slurry with a solid content of 65% is obtained. The positive electrode active material slurry is coated on the carbon layer and then placed in a vacuum drying oven and baked at 150 °C for 20 min to obtain an active material layer with a thickness of 100 μm; wherein, the mass percentage of polyvinylidene fluoride in the active material layer is 4%, the mass percentage of lithium cobaltate in the active material layer is 90%, and the mass percentage of carbon black in the active material layer is 6%;

[0076] Step 3: Add perovskite-type solid electrolyte (chemical formula: Li 0.33 La 0.56 TiO 3) The powder, polyvinylidene fluoride, and N-methylpyrrolidone are added to a stirring device and stirred at a revolution speed of 30 rpm and a rotation speed of 2000 rpm for 90 minutes. After uniform stirring, a solid electrolyte slurry with a solid content of 45% is obtained. The solid electrolyte slurry is coated on the active material layer and then placed in a vacuum drying oven and baked at 120 °C for 15 minutes to obtain a solid electrolyte layer with a thickness of 14 μm. Finally, a positive electrode plate of a lithium-ion battery is obtained. Among them, the mass percentage of polyvinylidene fluoride in the solid electrolyte layer is 8%, and the mass percentage of the Li 0.33 La 0.56 TiO 3 The mass percentage of the powder in the solid electrolyte layer is 92%.

[0077] Example 2

[0078] Step 1: Carbon nanotubes with a pore size of 2 nm and a porosity of 50%, polyvinylidene fluoride, and ethanol are added to a high-speed mixer, and the revolution speed of stirring is adjusted to 25 rpm and the rotation speed is 2400 rpm. The stirring time is 80 minutes. After uniform stirring, a carbon layer slurry with a solid content of 48% is obtained. Then it is coated on one side of the aluminum foil and subsequently placed in a vacuum drying oven and baked at 150 °C for 15 minutes to obtain a carbon layer with a thickness of 4 μm. Among them, the mass percentage of polyvinylidene fluoride in the carbon layer is 15%, and the mass percentage of the carbon nanotubes in the carbon layer is 85%.

[0079] Step 2: Lithium cobaltate, graphite, polyvinylidene fluoride, and N-methylpyrrolidone are added to a high-speed mixer at a revolution speed of 25 rpm and a rotation speed of 1800 rpm for 60 minutes to obtain a positive electrode active material slurry with a solid content of 72%. The positive electrode active material slurry is coated on the carbon layer and then placed in a vacuum drying oven and baked at 150 °C for 25 minutes to obtain an active material layer with a thickness of 100 μm. Among them, the mass percentage of polyvinylidene fluoride in the active material layer is 6%, the mass percentage of lithium cobaltate in the active material layer is 90%, and the mass percentage of graphite in the active material layer is 4%;

[0080] Step 3: Garnet-type solid electrolyte (chemical formula Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12) The powder, polytetrafluoroethylene, and N-methylpyrrolidone are added to a high-speed disperser and stirred at a revolution speed of 25 rpm and a rotation speed of 2000 rpm for 90 minutes to obtain a solid electrolyte slurry with a solid content of 53%. The solid electrolyte slurry is coated on the active material layer and then placed in a vacuum drying oven and baked at 120 °C for 10 minutes to obtain a solid electrolyte layer with a thickness of 16 μm. Finally, a positive electrode sheet of a lithium-ion battery is obtained. Among them, the mass percentage of polytetrafluoroethylene in the solid electrolyte layer is 10%, and the mass percentage of the powder in the solid electrolyte layer is 90%. 6.4 La 3 Zr 1.4 Ta 0.6 O 12 The mass percentage of the powder in the solid electrolyte layer is 90%.

[0081] Example 3

[0082] Step 1: Add graphene with a pore size of 10 nm and a porosity of 70%, polyvinylidene fluoride, and ethanol to a high-speed mixer, and adjust the revolution speed of stirring to 25 rpm and the rotation speed to 2400 rpm. Stir for 80 minutes. After stirring evenly, a carbon layer slurry with a solid content of 55% is obtained. Then it is coated on one side of the aluminum foil, and then the electrode sheet is placed in a tunnel kiln and baked at 150 °C for 5 minutes to obtain a carbon layer with a thickness of 8 μm. Among them, the mass percentage of polyvinylidene fluoride in the carbon layer is 20%, and the mass percentage of graphene in the carbon layer is 80%.

[0083] Step 2: Place lithium cobaltate, graphite, polytetrafluoroethylene, and N-methylpyrrolidone in a high-speed mixer and stir at a revolution speed of 20 rpm and a rotation speed of 2000 rpm for 60 minutes to obtain a positive electrode active material slurry with a solid content of 64%. The positive electrode active material slurry is coated on the carbon layer and then placed in a tunnel kiln and baked at 120 °C for 10 minutes to obtain an active material layer with a thickness of 120 μm. Among them, the mass percentage of polytetrafluoroethylene in the active material layer is 3%, the mass percentage of lithium cobaltate in the active material layer is 96%, and the mass percentage of graphite in the active material layer is 1%.

[0084] Step 3: Place NASICON-type solid electrolyte (chemical formula: Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3) The powder, polytetrafluoroethylene, and N-methylpyrrolidone are placed in a high-speed disperser and stirred at a revolution speed of 25 rpm and a rotation speed of 2000 rpm for 90 minutes to obtain a solid electrolyte slurry with a solid content of 60%. The solid electrolyte slurry is coated on the active material layer and then placed in a tunnel kiln and baked at 120 °C for 6 minutes to obtain a solid electrolyte layer with a thickness of 14 μm. Finally, a positive electrode sheet of a lithium-ion battery is obtained. Among them, the mass percentage of polytetrafluoroethylene in the solid electrolyte layer is 15%, and the mass percentage of the powder in the solid electrolyte layer is 85%. 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 The mass percentage of the powder in the solid electrolyte layer is 85%.

[0085] Example 4

[0086] Step 1: Activated carbon fibers with a pore size of 3 nm and a porosity of 30%, polytetrafluoroethylene, and ethanol are added to a double planetary mixer, and the revolution speed of the stirring is adjusted to 20 rpm and the rotation speed is adjusted to 2200 rpm. After stirring for 90 minutes and mixing evenly, a carbon layer slurry with a solid content of 56% is obtained. Then it is coated on one side of the aluminum foil, and then the electrode sheet is placed in a vacuum drying oven and baked at 170 °C for 3 minutes to obtain a carbon layer with a thickness of 6 μm. Among them, the mass percentage of polytetrafluoroethylene in the carbon layer is 10%, and the mass percentage of the activated carbon fibers in the carbon layer is 90%.

[0087] Step 2: Lithium cobaltate, activated carbon fibers, polytetrafluoroethylene, and N-methylpyrrolidone are placed in a double planetary mixer and stirred at a revolution speed of 25 rpm and a rotation speed of 1800 rpm for 60 minutes to obtain a positive electrode active material slurry with a solid content of 65%. The positive electrode active material slurry is coated on the carbon layer and then placed in a vacuum drying oven and baked at 80 °C for 25 minutes to obtain an active material layer with a thickness of 80 μm. Among them, the mass percentage of polytetrafluoroethylene in the active material layer is 4%, the mass percentage of lithium cobaltate in the active material layer is 90%, and the mass percentage of the activated carbon fibers in the active material layer is 6%.

[0088] Step 3: NASICON-type solid electrolyte (chemical formula: Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3)A powder, polytetrafluoroethylene, and N-methylpyrrolidone are placed in a double planetary mixer and stirred at a revolution speed of 25 rpm and a rotation speed of 2000 rpm for 90 min to obtain a solid electrolyte slurry with a solid content of 30%. The solid electrolyte slurry is coated on the active material layer and then placed in a vacuum drying oven and baked at 120 °C for 12 min to obtain a solid electrolyte layer with a thickness of 12 μm. Finally, a positive electrode sheet of a lithium-ion battery is obtained. Among them, the mass percentage of polytetrafluoroethylene in the solid electrolyte layer is 10%, and the mass percentage of Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 The mass percentage of the powder in the solid electrolyte layer is 90%.

[0089] Example 5

[0090] Step 1: Graphene with a pore size of 100 nm and a porosity of 80%, polytetrafluoroethylene, and ethanol are added to a double planetary mixer, and the revolution speed of stirring is adjusted to 35 rpm and the rotation speed is adjusted to 2200 rpm. After stirring for 90 min and mixing evenly, a carbon layer slurry with a solid content of 30% is obtained. Then it is coated on one side of the aluminum foil, and then the electrode sheet is placed in a vacuum drying oven and baked at 80 °C for 30 min to obtain a carbon layer with a thickness of 0.1 μm. Among them, the mass percentage of polytetrafluoroethylene in the carbon layer is 1%, and the mass percentage of graphene in the carbon layer is 99%.

[0091] Step 2: Lithium cobaltate, carbon black, polyvinylidene fluoride, and ethanol are placed in a double planetary mixer and stirred at a revolution speed of 25 rpm and a rotation speed of 3000 rpm for 30 min to obtain a positive electrode active material slurry with a solid content of 60%. The positive electrode active material slurry is coated on the carbon layer and then placed in a vacuum drying oven and baked at 100 °C for 25 min to obtain an active material layer with a thickness of 10 μm. Among them, the mass percentage of polyvinylidene fluoride in the active material layer is 1%, the mass percentage of lithium cobaltate in the active material layer is 92%, and the mass percentage of carbon black in the active material layer is 8%.

[0092] Step 3: The NASICON-type solid electrolyte (chemical formula: Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3)Powder, polyvinylidene fluoride, and N-methylpyrrolidone were placed in a double planetary mixer and stirred at a revolution speed of 25 rpm and a rotation speed of 2000 rpm for 90 minutes to obtain a solid electrolyte slurry with a solid content of 50%. The solid electrolyte slurry was coated on the active material layer and then placed in a vacuum drying oven and baked at 170 °C for 5 minutes to obtain a solid electrolyte layer with a thickness of 20 μm. Finally, a positive electrode sheet of a lithium-ion battery was obtained. Among them, the mass percentage of polyvinylidene fluoride in the solid electrolyte layer was 2%, and the mass percentage of Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 The mass percentage of the powder in the solid electrolyte layer was 98%.

[0093] Example 6

[0094] Step 1: Activated carbon with a pore size of 30 nm and a porosity of 60%, polytetrafluoroethylene, and ethanol were added to a double planetary mixer, and the revolution speed of stirring was adjusted to 35 rpm and the rotation speed was 200 rpm. After stirring for 150 minutes and mixing evenly, a carbon layer slurry with a solid content of 50% was obtained. Then it was coated on one side of the aluminum foil, and then the electrode sheet was placed in a vacuum drying oven and baked at 120 °C for 6 minutes to obtain a carbon layer with a thickness of 5 μm. Among them, the mass percentage of polytetrafluoroethylene in the carbon layer was 8%, and the mass percentage of activated carbon in the carbon layer was 92%.

[0095] Step 2: Lithium iron phosphate, graphene, polyvinylidene fluoride, and N-methylpyrrolidone were placed in a double planetary mixer and stirred at a revolution speed of 25 rpm and a rotation speed of 1800 rpm for 60 minutes to obtain a positive electrode active material slurry with a solid content of 75%. The positive electrode active material slurry was coated on the carbon layer and then placed in a vacuum drying oven and baked at 170 °C for 25 minutes to obtain an active material layer with a thickness of 20 μm. Among them, the mass percentage of polyvinylidene fluoride in the active material layer was 5%, the mass percentage of lithium iron phosphate in the active material layer was 85%, and the mass percentage of graphene in the active material layer was 10%.

[0096] Step 3: NASICON-type solid electrolyte (chemical formula: Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3)Powder, polyvinylidene fluoride, and N-methylpyrrolidone are placed in a double planetary mixer and stirred at a revolution speed of 25 rpm and a rotation speed of 2000 rpm for 90 minutes to obtain a solid electrolyte slurry with a solid content of 30%. The solid electrolyte slurry is coated on the active material layer and then placed in a vacuum drying oven and baked at 170 °C for 30 minutes to obtain a solid electrolyte layer with a thickness of 150 μm. Finally, a positive electrode sheet of a lithium-ion battery is obtained. Among them, the mass percentage of polyvinylidene fluoride in the solid electrolyte layer is 8%, and the mass percentage of Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 The mass percentage of the powder in the solid electrolyte layer is 92%.

[0097] Example 7

[0098] Step 1: A carbon molecular sieve with a pore size of 2 nm and a porosity of 30%, polyvinylidene fluoride, and ethanol are added to a double planetary mixer, and the revolution speed of the stirring is adjusted to 20 rpm and the rotation speed is 1000 rpm. The stirring time is 100 minutes. After stirring evenly, a carbon layer slurry with a solid content of 70% is obtained. Then it is coated on one side of the aluminum foil, and then the electrode sheet is placed in a vacuum drying oven and baked at 170 °C for 10 minutes to obtain a carbon layer with a thickness of 8 μm. Among them, the mass percentage of polyvinylidene fluoride in the carbon layer is 5%, and the mass percentage of the carbon molecular sieve in the carbon layer is 95%.

[0099] Step 2: Lithium titanate, activated carbon, polyvinylidene fluoride, and N-methylpyrrolidone are placed in a double planetary mixer and stirred at a revolution speed of 25 rpm and a rotation speed of 1500 rpm for 80 minutes to obtain a positive electrode active material slurry with a solid content of 45%. The positive electrode active material slurry is coated on the carbon layer and then placed in a vacuum drying oven and baked at 170 °C for 3 minutes to obtain an active material layer with a thickness of 10 μm. Among them, the mass percentage of polyvinylidene fluoride in the active material layer is 2%, the mass percentage of lithium titanate in the active material layer is 88%, and the mass percentage of activated carbon in the active material layer is 10%.

[0100] Step 3: The perovskite-type solid electrolyte (chemical formula Li 0.33 La 0.56 TiO 3)Powder, polyvinylidene fluoride, and ethanol are placed in a double planetary mixer and stirred at a revolution speed of 25 rpm and a rotation speed of 800 rpm for 120 minutes to obtain a solid electrolyte slurry with a solid content of 50%. The solid electrolyte slurry is coated on the active material layer and then placed in a vacuum drying oven and baked at 100 °C for 3 minutes to obtain a solid electrolyte layer with a thickness of 0.5 μm. Finally, a positive electrode sheet of a lithium-ion battery is obtained. Among them, the mass percentage of polyvinylidene fluoride in the solid electrolyte layer is 6%, and the mass percentage of the Li 0.33 La 0.56 TiO 3 The mass percentage of the powder in the solid electrolyte layer is 94%.

[0101] The following is a description of the comparative examples for comparison with the examples of the present invention.

[0102] Comparative Example 1

[0103] The difference between this comparative example and Example 1 is that no carbon layer is coated on the aluminum foil, and only the active material layer and the solid electrolyte layer are sequentially coated on the same side of the aluminum foil.

[0104] Testing and discussion:

[0105] The positive electrode sheets prepared in Example 1, Example 3, and Comparative Example 1 are assembled into coin cells, and then the cycle performance test is carried out. The specific assembly and test methods are as follows:

[0106] Assembly of coin cells: The positive electrode sheet, polypropylene separator, graphite negative electrode sheet, and 1 mol / L LiPF 6 electrolyte solution (the solvent is ethylene carbonate) are assembled into coin cells by a conventional method.

[0107] Testing method for coin cells: Constant current charging at a rate of 0.1C until the voltage reaches 4.6V, then standing for 5 minutes, and then constant current discharging at a rate of 0.1C until the voltage reaches 2.75V, and then standing for 5 minutes is a cycle of charge and discharge process, and 100 cycles of charge and discharge tests are carried out according to the above method.

[0108] Figure 3 is a comparative diagram of the cycle curves measured for the coin cells assembled with the positive electrode sheets prepared in Example 1, Example 3, and Comparative Example 1 of the present invention, as shown in Figure 3As shown, the capacity retention rates of the button cells assembled with the positive electrode sheets prepared in Example 1 and Example 3 are significantly better than those of Comparative Example 1. This shows that the cycling performance of the button cells assembled with the positive electrode sheets prepared in Example 1 and Example 3 is better. This is because, in the present invention, a carbon layer prepared from a porous carbon source is coated on the aluminum foil. The porous structure of the carbon layer enables the electrolyte to quickly enter the carbon layer, and then infiltrate the active material layer from one side of the carbon layer, increasing the contact area between the electrode liquid and the active material layer, enabling the electrolyte to uniformly infiltrate the active material layer, providing a transmission path for lithium ions in the electrolyte, reducing the interfacial resistance caused by uneven infiltration, and thus improving the cycling performance of the battery.

[0109] The positive electrode sheet of the lithium ion battery provided by the present invention coats a carbon layer prepared from a porous carbon source on the aluminum foil to increase the contact area between the electrolyte and the active material layer, enabling the electrolyte to uniformly infiltrate the active material layer, providing a smooth transmission path for lithium ions, reducing the interfacial resistance caused by uneven infiltration, and improving the cycling performance of the battery. Applying the positive electrode sheet of the lithium ion battery provided by the invention to a lithium ion battery can enable the battery to have good cycling life and safety performance.

[0110] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A positive electrode sheet for a lithium-ion battery, characterized in that, the positive electrode sheet for the lithium-ion battery sequentially includes an aluminum foil, a carbon layer, an active material layer, and a solid electrolyte layer; wherein, the carbon layer includes a porous carbon source and a first binder, the pore size of the porous carbon source is 2 nm - 100 nm, and the porosity is 30% - 85%; the active material layer includes a positive electrode active material, a conductive agent, and a second binder; the solid electrolyte layer includes a solid electrolyte and a third binder; the carbon layer is used to increase the contact area between the electrolyte and the active material layer, so that the electrolyte can uniformly infiltrate the active material layer, provide a smooth transmission path for lithium ions, reduce the interfacial resistance caused by uneven infiltration, and improve the cycle performance of the battery.

2. The positive electrode sheet for a lithium-ion battery according to claim 1, characterized in that, the percentage of the mass of the first binder in the mass of the carbon layer is 1% - 20%, and the percentage of the mass of the porous carbon source in the mass of the carbon layer is 80% - 99%; the percentage of the mass of the second binder in the mass of the active material layer is 1% - 6%, the percentage of the mass of the positive electrode active material in the mass of the active material layer is 85% - 96%, and the percentage of the mass of the conductive agent in the mass of the active material layer is 1% - 10%; the percentage of the mass of the third binder in the mass of the solid electrolyte layer is 2% - 15%, and the percentage of the mass of the solid electrolyte in the mass of the solid electrolyte layer is 85% - 98%.

3. The positive electrode sheet for a lithium-ion battery according to claim 1, characterized in that, the thickness of the carbon layer is 0.1 μm - 20 μm; the thickness of the active material layer is 10 μm - 150 μm; the thickness of the solid electrolyte layer is 0.1 μm - 30 μm.

4. The positive electrode sheet for a lithium-ion battery according to claim 1, characterized in that, the porous carbon source includes one or more of activated carbon, activated carbon fiber, carbon molecular sieve, graphene, acetylene black, carbon nanotube; the positive electrode active material includes one or more of lithium cobaltate, lithium manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium titanate, nickel cobalt manganese ternary material; the conductive agent includes one or more of graphite, carbon black, activated carbon, activated carbon fiber, carbon molecular sieve, graphene, acetylene black, carbon nanotube; the solid electrolyte includes one or more of perovskite-type solid electrolyte, NASICON-type solid electrolyte, LISICON-type solid electrolyte, garnet-type solid electrolyte; the first binder includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, polyolefins, polyvinyl alcohol, polyacrylic acid, polyurethane; the second binder includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, polyolefins, polyvinyl alcohol, polyacrylic acid, polyurethane; the third binder includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, polyolefins, polyvinyl alcohol, polyacrylic acid, polyurethane.

5. A method for preparing a positive electrode sheet of a lithium-ion battery according to any one of claims 1-4 above, characterized in that, the preparation method includes: Adding a porous carbon source, a first binder and a first solvent into a stirring device. After stirring evenly, a carbon layer slurry with a solid content of 30%-70% is obtained. Coating the carbon layer slurry on one side of an aluminum foil, and placing the coated aluminum foil in a drying device to bake at 80°C-170°C for 3 min-30 min to obtain a carbon layer; wherein, the pore diameter of the porous carbon source is 2 nm-100 nm, and the porosity is 30%-85%; Adding a positive electrode active material, a conductive agent, a second binder and a second solvent into a stirring device. After stirring evenly, a positive electrode active material slurry with a solid content of 45%-75% is obtained. Coating the positive electrode active material slurry on the carbon layer, and baking at 80°C-170°C for 3 min-30 min in a drying device to obtain an active material layer; Adding a solid electrolyte, a third binder and a third solvent into a stirring device. After stirring evenly, a solid electrolyte slurry with a solid content of 30%-70% is obtained. Coating the solid electrolyte slurry on the active material layer, and baking at 80°C-170°C for 3 min-30 min in a drying device to obtain a solid electrolyte layer, and finally obtaining the required positive electrode sheet of the lithium-ion battery.

6. The preparation method according to claim 5, characterized in that, the percentage of the mass of the first binder in the mass of the carbon layer is 1%-20%, and the percentage of the mass of the porous carbon source in the mass of the carbon layer is 80%-99%; the percentage of the mass of the second binder in the mass of the active material layer is 1%-6%, the percentage of the mass of the positive electrode active material in the mass of the active material layer is 85%-96%, and the percentage of the mass of the conductive agent in the mass of the active material layer is 1%-10%; the percentage of the mass of the third binder in the mass of the solid electrolyte layer is 2%-15%, and the percentage of the mass of the solid electrolyte in the mass of the solid electrolyte layer is 85%-98%.

7. The preparation method according to claim 5, characterized in that, the porous carbon source includes one or more of activated carbon, activated carbon fiber, carbon molecular sieve, graphene, acetylene black, carbon nanotube; the positive electrode active material includes one or more of lithium cobaltate, lithium manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium titanate, nickel cobalt manganese ternary material; the conductive agent includes one or more of graphite, carbon black, activated carbon, activated carbon fiber, carbon molecular sieve, graphene, acetylene black, carbon nanotube; the solid electrolyte includes one or more of perovskite-type solid electrolyte, NASICON-type solid electrolyte, LISICON-type solid electrolyte, garnet-type solid electrolyte; the first binder includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, polyolefins, polyvinyl alcohol, polyacrylic acid, polyurethane; The second binder includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, polyolefins, polyvinyl alcohol, polyacrylic acid, polyurethane; The third binder includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, polyolefins, polyvinyl alcohol, polyacrylic acid, polyurethane; The first solvent includes one or more of N-methylpyrrolidone, dimethyl carbonate, methanol, ethanol, propanol, butanol, isopropanol; The second solvent includes one or more of N-methylpyrrolidone, dimethyl carbonate, methanol, ethanol, propanol, butanol, isopropanol; The third solvent includes one or more of N-methylpyrrolidone, dimethyl carbonate, methanol, ethanol, propanol, butanol, isopropanol.

8. The preparation method according to claim 5, wherein, when preparing the carbon layer slurry, the revolution speed of the stirring equipment is 20 rpm - 35 rpm, the rotation speed is 200 rpm - 3000 rpm, and the stirring time is 30 min - 150 min; when preparing the positive active material slurry, the revolution speed of the stirring equipment is 20 rpm - 35 rpm, the rotation speed is 200 rpm - 3000 rpm, and the stirring time is 30 min - 150 min; when preparing the solid electrolyte slurry, the revolution speed of the stirring equipment is 20 rpm - 35 rpm, the rotation speed is 200 rpm - 3000 rpm, and the stirring time is 30 min - 150 min.

9. The preparation method according to claim 5, wherein, the thickness of the carbon layer is 0.1 μm - 20 μm; the thickness of the active material layer is 10 μm - 150 μm; the thickness of the solid electrolyte layer is 0.1 μm - 30 μm.

10. A lithium-ion battery, wherein, the lithium-ion battery includes the lithium-ion battery positive electrode sheet according to any one of claims 1 - 4 or the lithium-ion battery positive electrode sheet prepared by the preparation method according to any one of claims 5 - 8.

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