Method for forming high-capacity lithium iron phosphate lithium ion battery

Abstract

The invention relates to a method for forming a high-capacity lithium iron phosphate lithium ion battery, belonging to the technical field of manufacturing of lithium iron batteries. The method is characterized by comprising the following steps of: firstly, trickle charging, namely carrying out constant-voltage charging until the current is 0.02-0.05C while the charging cutoff voltage is 3.55-3.6V, and then carrying out constant-current discharging at small current; secondly, bulk charging, namely carrying out constant-voltage charging until the current is 0.02-0.05C while the charging cutoff voltage is 3.75-4.0V, and then carrying out the constant-current discharging at small current; and thirdly, trickle charging while the charging cutoff voltage is 3.55-3.6V, thus the lithium ion battery is formed. In the invention, the charging cutoff voltage in the step 1 is limited, thus metal lithium can be prevented from being crystallized at a cathode and the safety of the battery is enhanced; the bulk charging is carried out in the step 2, thus side reaction of the carbon cathode can be complete; and the trickle charging is carried out in the step 3, a stable solid electrolyte membrane can be conveniently formed, and the stability and the cycle performance of the battery can be enhanced.

Description

technical field [0001] The invention relates to a method for forming a lithium-ion battery, in particular to a method for forming a large-capacity lithium iron phosphate lithium-ion battery. Background technique [0002] At present, large-capacity lithium iron phosphate lithium-ion secondary batteries are widely used in small power plants, hybrid electric vehicles, pure electric buses and other fields due to their excellent charge and discharge characteristics, high safety and stable cycle performance. However, under the current existing material system and production process, the pursuit of energy density is too high, and the only way to increase the capacity of lithium iron phosphate single battery and improve the ratio of battery positive and negative electrode material capacity, especially the change of the latter, in the formation In the process, due to the improper setting of the upper limit of the low-current constant-current charging voltage, the possibility of the p...

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Problems solved by technology

However, under the current existing material system and production process, the pursuit of energy density is too high, and the only way to increase the capacity of lithium iron phosphate single battery and improve the ratio of battery positive and negative electrode material capacity, especially the change of the latter, in the formation In the process, due to the improper setting of the upper limit of the low-current constant-current charging voltage, the possibility of the precipitation of lithium metal crystals on the negative electrode will increase; at the same time, due to the change in the volume of the negative electrode and the cracking of the particles during the later high-current charging process, a new surface will be formed. The liquid reacts chemically to form a new solid electrolyte film, which generates gas and destroys the formed solid electrolyte film, thereby greatly reducing the safety and stability of the battery, which in turn affects the overall performance of the battery, which is not conducive to the market application of lithium iron phosphate batteries

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