Negative pole sheet, preparation method thereof, lithium ion battery, preparation method of lithium ion battery and application of lithium ion battery

Abstract

The invention belongs to the field of batteries and provides a negative pole sheet, a manufacturing method thereof, a lithium ion battery, a preparation method of the lithium ion battery and application of the lithium ion battery. The negative pole sheet comprises a negative pole current collector and negative pole active material layers coating the surface of the negative pole current collector;the negative pole active material layers comprise three layers distributed from inside to outside; the particle sizes of the negative pole active materials of the three negative pole active material layers are different and are sequentially increased from inside to outside; the negative pole active material of the first negative pole active material layer is artificial graphite having D50 of 5-10micrometers; the negative pole active material of the second negative pole active material layer is artificial graphite having D50 of 8-12 micrometers; and the negative pole active material of the third negative pole active material layer is artificial graphite having D50 of 10-15 micrometers. The lithium ion battery provided by the invention can realize rapid charging of 3.2 C or above; the massenergy density of the battery is higher than 260Wh/kg; the capacity retention ratio of the battery under the condition of 2000 times of 3.2 C quick charging is more than 80%; and the requirements of electric vehicles on quick charging enabling 80% SOC within 15 min, high endurance and a long life cycle are met.

Description

technical field [0001] The invention relates to a negative electrode sheet and a preparation method thereof, a lithium ion battery, a preparation method and application thereof. Background technique [0002] As a new type of green power supply, lithium-ion batteries have the advantages of small self-discharge rate, high specific energy, high open circuit voltage, and no memory effect. They are widely used in mobile phones, notebook computers and other digital products, pure electric and hybrid new energy vehicles. . For new energy vehicles, the energy density and charging time of the battery are two important technical indicators. However, the charging time of existing new energy vehicles is too long, which seriously affects the customer's car experience and limits the popularization of new energy vehicles. . Improving the energy density of the battery, improving the battery life of the car, and realizing the fast charging of the battery at the same time play a vital role ...

AI Technical Summary

Problems solved by technology

[0003] At present, there are also some methods that can realize fast charging of lithium-ion batteries. For example, CN105932349A discloses an improved single-particle model for lithium-ion batteries, and finally obtains the lithium intercalation rate on the surface of the negative electrode active material and the set threshold by using theoretical analysis methods. The relationship between the size of the battery, so as to control the battery charging current and charging time to achieve fast charging of the lithium-ion battery, but this is only a theoretical optimization of the charging strategy of the lithium-ion battery, applied to the complex chemical system in the lithium-ion battery, its actual The effect of fast charging is unknown

[0004] CN105489857A discloses a lithium-ion battery for rapid charging, which is characterized in that the negative electrode active material is modified graphite with a medium particle diameter D50 of 3 μm to 20 μm, and the modified graphite uses pitch powder as raw material, and the wire is spun under a magnetic field After carbonization, a carbon fiber structure that is conducive to the rapid diffusion of lithium ions and has excellent high-current charging capacity is obtained, and the carbon microspheres formed by pyrolysis and activation with phenolic resin as raw material are compositely embedded, and then the surface is formed by pyrolysis of phenolic resin particles. The low-crystalline carbon coating layer, which makes the intercalation of lithium ions easier and faster, improves the diffusion rate of lithium ions. The disclosed lithium-ion battery can be charged to more than 90% of the battery capacity when charged at 30C for 2 minutes , to achieve fast charging, but its data is only the data of small capacity (below 3Ah) batteries, which cannot meet the fast charging requirements of high energy density batteries, and it has strict requirements on raw materials, and the preparation of raw materials is complicated

[0005] CN104347880A discloses a lithium-ion battery that can be quickly charged, and is characterized in that the positive electrode active material includes component A and component B, and component A is selected from nickel-cobalt lithium aluminate, nickel-cobalt lithium manganate, lithium manganate and At least one of lithium cobaltate, component B is selected from at least one of lithium iron phosphate and lithium titanate, the use of this mixed positive electrode material prolongs the time of low-voltage constant current charging and improves the charging speed, but the positive electrode used in this method The active substance is two kinds of materials with different properties. Only through simple blending, in the actual use process, it is easy to cause the collapse of a certain material structure, and its cycle life cannot be guaranteed.

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