Method for processing positive electrode material of lithium nickel manganese oxide battery

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a processing method of a lithium nickel manganese oxide battery positive electrode material. Preparing 86%-97% of a positive electrode material, 1%-5% of a conductive agent and 2%-9% of glue into positive electrode slurry; the viscosity of the positive electrode slurry is 1000 to 10000 centipoises; filling the prepared positive electrode slurry into a three-dimensional grid of a foamed aluminum current collector in an extrusion manner; the three-dimensional copper-clad foamed aluminum structure on the negative electrode side has a large number of pores, volume expansion can be allowed when a negative electrode material is embedded into lithium, the overall structure of the device is protected against deformation, and the service life is prolonged by 200-300%.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and particularly to a processing method for the positive electrode material of a lithium nickel manganate battery. Background Art

[0002] Lithium-ion batteries have the advantage of a large energy storage density and are widely used in vehicle power batteries and mobile electronic consumer products. They are an important part of new energy. After years of development, mature positive electrode materials containing lithium compounds and negative electrode materials made of various types of graphite-like carbon have been formed for lithium-ion batteries. And a relatively mature processing method has been formed, that is, the positive electrode material is mixed with a conductive agent, a binder, etc. to form a slurry, which is coated and roll-pressed together. After curing, it is tightly adhered to the aluminum foil. The negative electrode material is mixed with a binder to form a slurry, which is coated and roll-pressed together. After curing, it is tightly adhered to the copper foil. Then the tab is welded, separated by a separator, and the electrolyte is injected to form a finished battery. Currently, the development trend of lithium-ion batteries is to increase the energy density as much as possible without losing its power density. However, for the foil electrode, it means increasing the thickness of both the positive electrode and the negative electrode at the same time, bringing serious problems of electronic polarization and ionic polarization. At the same time, the thermal conductivity of the electrode is not high, and when charging at high power or high current, it often leads to accidents such as heating, thermal runaway, electrolyte decomposition, fire, combustion or explosion.

[0003] It has been reported that the positive electrode material can be filled in a three-dimensional aluminum foam current collector to form a thicker electrode, improving the energy density on the positive electrode side and maintaining the power density. For a similar idea, it seems that a copper foam current collector can be used on the negative electrode side to improve the performance of the negative electrode. However, due to the preparation process, the copper foil can be as thin as a few micrometers, while the copper foam is relatively thick. Therefore, using copper foam on the negative electrode will greatly increase the weight of the device and reduce the energy density of the device. Although aluminum foam is much lighter than copper foam, it cannot be used because aluminum is unstable on the negative electrode side.

[0004] There have been some reports on using all-carbon current collectors. However, such materials have poor welding polarity, poor repeatability of the preparation process, are prone to deformation in the electrolyte, cannot withstand roll-pressing, and do not have the consistency for large-scale industrial sheet processing.

[0005] Therefore, there is an urgent need to provide a high-energy lithium-ion battery with a novel structure. Summary of the Invention

[0006] The technical problem to be solved by the present invention is: overcoming the deficiencies of the prior art, the present invention provides a high-energy lithium-ion battery and its preparation method to solve at least one technical problem in the prior art.

[0007] To achieve the above object, the present invention also protects a processing method for the positive electrode material of a nickel manganese acid lithium battery. The method includes: making a positive electrode slurry by mixing 86%-97% of the positive electrode material, 1%-5% of a conductive agent, and 2%-9% of a binder; the viscosity of the positive electrode slurry is 1000-10000 centipoise; using an extrusion method to fill the made positive electrode slurry into the three-dimensional grid of an aluminum foam current collector; making the positive electrode slurry in close contact with the three-dimensional grid of the aluminum foam current collector through roll pressing; drying for 1-20 hours at a temperature of 100-150°C to form a positive electrode plate; making a negative electrode slurry by mixing 86%-97% of the negative electrode material, 1%-5% of a conductive agent, and 2%-9% of a binder; the viscosity of the negative electrode slurry is 1000-10000 centipoise; determining the amount of the negative electrode slurry according to the capacity of the positive electrode slurry of the positive electrode plate, and filling the negative electrode slurry into the three-dimensional grid of a copper-clad aluminum foam current collector; making the negative electrode slurry in close contact with the three-dimensional grid of the copper-clad aluminum foam current collector through roll pressing; drying for 1-20 hours at a temperature of 100-150°C to form a negative electrode plate with a set thickness; cutting the negative electrode plate so that the size of the negative electrode plate is adapted to the size of the positive electrode plate; coating the side surface of the cut negative electrode plate with a binder and heating and curing it; respectively welding a positive electrode tab and a negative electrode tab to the positive electrode plate and the negative electrode plate, separating them with a separator, and assembling multiple pieces; encapsulating the assembled electrode plates in a pre-stamped shell, injecting electrolyte after dehydration and degassing steps, and performing aging and encapsulation to form a lithium-ion battery product. Further, preferably, the conductive agent used in the positive electrode slurry is one or more of carbon nanotubes, carbon black, and graphene; the conductive agent used in the negative electrode slurry is one or more of carbon nanotubes, carbon black, and graphene.

[0008] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0009] 1) Using a copper-clad aluminum foam current collector on the negative electrode side can not only be well matched with the positive electrode using an aluminum foam current collector, but also, due to its lower density than copper foil or copper foam, the energy density of the device is increased by 5-25%; and a large amount of copper resources are saved.

[0010] 2) The copper-clad aluminum foam current collector on the negative electrode side provides a three-dimensional conductive and heat-conducting method, making the internal temperature of the device more uniform during rapid charging and discharging. At the same time, it avoids being corroded by the electrolyte, and the service life of the device is increased by 30-50%.

[0011] 3) Copper-clad aluminum foam has both chemical stability and processing rigidity, and is easier to implement industrially than a fully carbon current collector; it has the characteristics of high product consistency and a 80% reduction in manufacturing cost.

[0012] 4) The three-dimensional copper-coated aluminum foam structure on the negative electrode side has a large number of pores, which can allow the volume expansion when the negative electrode material embeds lithium, protecting the overall structure of the device from deformation and extending the service life by 200-300%. Detailed implementation manners

[0013] The present invention will be further described below in conjunction with embodiments:

[0014] Embodiment 1

[0015] 91% of the positive electrode material (lithium iron phosphate, average particle size 0.2-10 microns), 5% of the conductive agent (carbon nanotubes) and 4% of the adhesive are made into a positive electrode paste (viscosity 6000 centipoise); by extrusion, it is filled into the three-dimensional grid of the aluminum foam current collector (porosity 95%), and by rolling, the two are made to be in close contact. It is dried at 100 °C for 20 hours to form a positive electrode sheet. The thickness is 100 microns and the areal density is 90 mg / cm2. 94% of the negative electrode material (graphite, particle size 5-10 microns), 3% of the conductive agent (carbon black) and 3% of the adhesive are made into a negative electrode paste (viscosity 10000 centipoise). According to the capacity of the positive electrode sheet, the amount of the negative electrode material is determined, and it is filled into the three-dimensional grid of the copper-coated aluminum foam current collector (porosity 93%), and by rolling, the two are made to be in close contact, and it is dried at 100 °C for 10 hours to form a negative electrode sheet with a controllable thickness. For the side surface of the cut negative electrode sheet (aluminum may be exposed), it is coated with an adhesive and heated and cured for protection.

[0016] It should be noted that the positive electrode material can be but is not limited to lithium-containing compounds capable of undergoing bulk redox charging and lithium-containing compounds doped with carbon materials, such as one or more of lithium iron phosphate and its doped materials, lithium manganate and its doped materials, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium-rich solid solution materials, polyanion materials (such as orthosilicate lithium ion type, lithium titanium phosphate type, etc.), and their necessary carbon-coated compounds), as well as carbon materials for the conductive agent. The negative electrode material can be but is not limited to graphite, graphite-like carbon, mesocarbon microbeads, silicon, tin, silicon-carbon materials, silicon-oxygen-carbon materials, lithium titanate, metallic lithium materials, etc., as well as carbon materials for the conductive agent. The particle size of the electrode material is 0.01-10 microns.

[0017] The length and width dimensions of the negative electrode sheet are the same as those of the positive electrode sheet, and in terms of capacity, the capacity ratio of the negative electrode sheet to the positive electrode sheet is 1.01:1.

[0018] Weld the positive electrode tab (which can be aluminum, steel, nickel, etc., aluminum in this embodiment) and the negative electrode tab (copper) respectively on the tab welding areas of the positive electrode plate and the negative electrode plate; separate them with a separator and assemble multiple pieces; stamp an aluminum-plastic film or a metal shell to form a housing, encapsulate the assembled electrode plates in the housing, inject an electrolyte (lithium hexafluorophosphate type electrolyte) after dehydration and degassing steps, and perform aging and encapsulation to form a lithium-ion battery product. It should be noted that a sufficient area is directly left on the aluminum foam positive electrode plate and welded to a metal tab (made of materials such as aluminum, steel, nickel, etc.) after pressing. A sufficient aluminum foam area is directly left on the copper-coated aluminum foam negative electrode plate and welded to a copper tab after pressing.

[0019] Through testing, it is found that compared with the same-weight battery using a copper foil current collector, the obtained lithium-ion battery has an energy density increased by 5% and a device life increased by 30%.

[0020] In the present invention, the description of the direction and relative position relationship of the structure, such as the description of front, back, left, right, up, and down, does not constitute a limitation to the present invention and is only for convenience of description.

Claims

1. A processing method for the positive electrode material of a nickel-manganese acid lithium battery, characterized in that, the method comprises, making a positive electrode slurry from 86%-97% of the positive electrode material, 1%-5% of the conductive agent and 2%-9% of the binder; the viscosity of the positive electrode slurry is 1000-10000 centipoises; using an extrusion method to fill the made positive electrode slurry into the three-dimensional grid of the aluminum foam current collector; making the positive electrode slurry in close contact with the three-dimensional grid of the aluminum foam current collector by roll pressing; drying for 1-20 hours under the condition that the temperature is 100-150 °C to form a positive electrode plate; making a negative electrode slurry from 86%-97% of the negative electrode material, 1%-5% of the conductive agent and 2%-9% of the binder; the viscosity of the negative electrode slurry is 1000-10000 centipoises; determining the amount of the negative electrode slurry according to the capacity of the positive electrode slurry of the positive electrode plate, filling the negative electrode slurry into the three-dimensional grid of the copper-clad aluminum foam current collector; making the negative electrode slurry in close contact with the three-dimensional grid of the copper-clad aluminum foam current collector by roll pressing; drying for 1-20 hours under the condition that the temperature is 100-150 °C to form a negative electrode plate with a set thickness; cutting the negative electrode plate so that the size of the negative electrode plate is adapted to the size of the positive electrode plate; coating the side surface of the cut negative electrode plate with a binder and heating and curing it; welding the positive electrode tab and the negative electrode tab to the positive electrode plate and the negative electrode plate respectively, separating them with a separator, and assembling multiple pieces; encapsulating the assembled plates in a pre-stamped shell, injecting electrolyte after dehydration and degassing steps, and performing aging and encapsulation to form a lithium-ion battery product.

2. The processing method for the positive electrode material of a nickel-manganese acid lithium battery according to claim 2, characterized in that, the conductive agent used for the positive electrode slurry is one or more of carbon nanotubes, carbon black and graphene; the conductive agent used for the negative electrode slurry is one or more of carbon nanotubes, carbon black and graphene.