Method for increasing energy density of lithium ion battery and prolonging cycle life of lithium ion battery

Abstract

The invention relates to the field of lithium ion batteries, in particular to a high-energy lithium ion phosphate battery, and aims at providing a method for increasing the capacity of a lithium ion phosphate battery, actually achieving the gram capacity of a lithium ion phosphate cathode material, enabling the capacity not to be reduced in the cyclic process, increasing the energy density of the lithium ion phosphate battery and prolonging the cycle life of the lithium ion phosphate battery. In the manufacturing process of the lithium ion battery, an active lithium material is added and supplemented into an active cathode material to form a mixed material, the gram capacity of the mixed material is improved, and the effective active lithium amount supplied by the supplemented active lithium material accounts for 1%-25% of the active lithium amount of the anode capacity; the supplemented active lithium material needs to be subjected to lithium removal, and the structure collapses after lithium removal, that is to say, the initial charge cut-off voltage is set as the voltage needed when the material is completely subjected to lithium removal until the material is in an irreversible state. The method has the advantages of being simple in process, convenient to operate and the like.

Description

technical field [0001] The invention relates to the field of lithium-ion batteries, in particular to a high-energy lithium-ion battery. Background technique [0002] Lithium-ion battery refers to a type of lithium-ion battery that uses lithium-ion batteries as the positive electrode material. It has attracted the attention of the industry due to its outstanding features such as long life, high safety and stability, wide operating temperature range, and extensive material sources, especially power batteries. aspect. However, lithium-ion batteries also have their disadvantages, mainly because the working voltage is low, only 3.2V. Compared with the 3.7V of other commonly used lithium-ion cathode materials, the tap density is 1.0-1.4g / cm2 smaller. 3 , which causes the energy density of lithium-ion batteries to be low. Currently, the highest single lithium iron phosphate battery model is 26650 cylindrical batteries, and the energy density is only 140.9wh / Kg. The battery capacit...

AI Technical Summary

Problems solved by technology

The film formation on the surface of the graphite negative electrode and the high-order lithium stored are all derived from the active lithium of the positive electrode material, and the first-time efficiency of the lithium iron phosphate positive electrode material is very high, basically close to 100%, and many materials can reach 155-163mAh / g. The graphite negative electrode The active lithium needed to form the SEI film comes from the reversible part of the positive electrode material, resulting in a decrease in the actual capacity of the positive electrode of the lithium-ion battery, generally only 125-140mAh / g

For a full battery, the capacity drops by 8% to 14%, resulting in a decrease in the energy density of the battery

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