Preparation method of fast-chargeable high-rate lithium iron phosphate battery

Abstract

The invention provides a method for preparing a fast-chargeable high-rate lithium iron phosphate battery, comprising: making a positive pole piece: 85%-95% by weight of positive active material, 1%-10% of conductive agent and 1% - Dissolve 15% of the binder in the solvent to make the positive electrode slurry, use 8~20μm aluminum foil as the current collector, apply the positive electrode slurry on the aluminum foil and dry it to make the pole piece; make the negative pole piece: use 90% -98% by weight of the negative electrode active material, 1%-5% of the conductive agent and 1%-5% of the binder are dissolved in the solvent to make the negative electrode slurry, and the copper foil of 6~20μm is used as the current collector, and the negative electrode slurry is The material is coated on a copper foil and dried to make a negative electrode sheet. The beneficial effect of the invention is that the high-rate lithium iron phosphate battery, the charging rate is increased from the conventional 1C to over 5C, the battery can be charged to 90% of the nominal capacity of the battery in 10 minutes, and the battery can be fully charged within 15 minutes in the shortest charging time.

Description

technical field [0001] The invention relates to a lithium ion battery, in particular to a preparation method of a fast-chargeable high-rate lithium iron phosphate battery. Background technique [0002] Lithium-ion batteries have the characteristics of high specific energy, high voltage platform, long cycle life, wide operating temperature range, no memory effect, and environmental friendliness. At present, it has been widely used in 3C digital portable electrical appliances such as mobile phones, notebook computers, and electronic instruments, and has gradually expanded to electric tools and electric vehicles. Therefore, the charging performance of lithium-ion batteries has been proposed With higher requirements, it is hoped that there will be a breakthrough in the high-rate fast charging to reduce the battery charging time. [0003] At present, the material system used in lithium-ion batteries is mainly lithium cobalt oxide (LiCoO 2 ), lithium manganate (LiMn 2 o 4 ), n...

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Problems solved by technology

[0003] At present, the material system used in lithium-ion batteries is mainly lithium cobalt oxide (LiCoO 2 ), lithium manganate (LiMn 2 o 4 ), nickel-cobalt-manganese ternary material (LiNi 1-x-y co x wxya 2 ) and lithium iron phosphate (LiFePO 4 ), lithium cobaltate and nickel-cobalt-manganese ternary materials have the presence of Co element, and its own structure determines that its surface temperature will rise sharply in high-rate charging, and there are certain safety hazards, which directly restrict its application in high-rate fields; manganic acid The safety performance of lithium is relatively good, but its wide application is also restricted due to its limited cycle life (generally only 300 weeks) and poor high temperature performance; while LiFePO 4 With its excellent safety performance and good cycle life, it has certain advantages in the field of fast-chargeable lithium-ion batteries

[0004] However, lithium iron phosphate also has its own disadvantages. For example, the conductivity of lithium iron phosphate is relatively low, which directly restricts its high-rate use requirements, which requires that LiFePO 4 Modified to improve its high rate charge and discharge performance

For example, the use of crystal phase control to obtain nano-scale LiFePO 4 , but the LiFePO prepared by this method 4 The specific surface area of ​​the material is large, the processing performance is poor, the dispersion of the slurry is difficult, and the powder or material drop of the pole piece is prone to occur in the coating and assembly process, and the manufacturing cost will also increase sharply due to the complicated process; if using Carbon coating to obtain LiFePO 4 / carbon composite materials, although this method is simple and easy in technology, the material prepared by this method has a high carbon content, which greatly reduces the content of active materials, which is not conducive to the improvement of battery energy density

However, the above methods mostly shorten the Li + The transmission path to improve the high rate performance of the battery, and for LiFePO 4 The conductivity itself has not been significantly improved, and the final improvement after the battery is made is often the high-rate discharge performance of the lithium iron phosphate battery, while its high-rate charge performance has not been significantly improved.