CN-108963366-B - Lithium battery and pre-charging method of series battery pack thereof

Abstract

The invention discloses a lithium battery and a pre-charging method of a serial battery pack thereof. Through once little electric current charge, can make battery negative pole surface form stable SEI membrane, improve the cycle life of battery, carry out once again heavy current charge, improve charging efficiency, in heavy current charging process, change the size of charging current along with battery voltage's change, make charging current size adapt to the charge capacity of battery, reduce the damage to battery material, adopt once little electric current constant voltage charge at last, can prevent the problem that lithium analysis appears on the battery pole piece. When the series battery pack is charged, the current in the heavy current charging stage is calculated according to the maximum voltage of the single batteries in the battery pack, so that the consistency of the single batteries in the battery pack can be improved, the damage caused by too fast charging of partial batteries due to the inconsistency of the batteries is reduced, and the service life of the series battery pack is prolonged.

Inventors

• YU HUACHAO
• HOU FENG
• LAN YUXIA
• JIANG CAIHONG
• WANG YUJIAO

Assignees

• 深圳市比克动力电池有限公司
• 深圳市比克动力电池有限公司

Dates

Publication Date

20260421

Application Date

20180730

Priority Date

20180730

Claims (1)

1. 1. A method for precharging a lithium battery serial battery pack comprises the following steps of S01, constant-current charging is carried out on the serial battery pack by adopting a current I0, the battery pack is charged until the average voltage of the single batteries in the serial battery pack is a voltage U1, then the battery pack is kept stand for 3-6min, S02, starting from the voltage U1, the battery pack is charged by adopting the current I1 as an initial current, voltage data of the single batteries in the serial battery pack are respectively sampled in the charging process, when the voltage data difference of the single batteries which are continuously sampled twice is a set value DeltaU, the current is regulated to a current I5, the battery pack is continuously charged until the minimum voltage of the single batteries in the serial battery pack is a charging voltage target value U0 of the single batteries, S03, constant-voltage charging is carried out on the serial battery pack by adopting a current I3 and a voltage U0, and the precharging of the serial battery pack is completed by adopting a current I4, wherein the current I5 = I1-3 x (U3/U0) x 0, and the current I3 is the maximum value of the voltage of the single batteries in the serial battery pack when the voltage data is sampled each time; The current I0 is 0.1-0.4C, the current I1 is 0.5-2.5C, the sampling period of voltage U2 data is 0.1-0.5s, the current I3 is 0.1-0.4C, the cut-off current I4 is 0.01-0.05C, the difference (U0-U1) between the charging voltage target value U0 and the voltage U1 is 0.5-1.8V, and the set value DeltaU is 0.03-0.05V.

Description

Lithium battery and pre-charging method of series battery pack thereof Technical Field The invention belongs to the field of lithium battery charging, and particularly relates to a lithium battery and a pre-charging method of a series battery pack thereof. Background The lithium ion battery is a secondary battery, has the advantages of high energy density, long service life, high rated voltage, low self-discharge rate, green and environment-friendly property and the like, and is widely applied to new energy automobiles, power grid energy storage and digital products. The market demand of new energy products is increasing nowadays, the requirements on battery manufacturers are also increasing, the production efficiency of the batteries is also improved while the product quality is ensured, and the production capacity is increased. This requires optimisation of existing production processes. Pre-charging, an important step in the manufacturing process of lithium batteries, can directly affect the electrochemical performance and the service life of lithium batteries. In general, the precharge process takes much time, and the production cycle of the lithium battery is prolonged. In the precharge process, if the precharge time can be shortened without affecting the battery performance, the production efficiency of the battery can be effectively improved. In the first charging process, a layer of solid electrolyte interface film (SEI film) is formed on the surface of the battery cathode, and the interface film is a passivation film and has the characteristic of being insoluble in organic solvents, can exist stably in the organic solvents, can effectively prevent co-intercalation of solvent molecules, avoids damage to electrode materials caused by co-intercalation of the solvent molecules, and greatly prolongs the service life and the cycle performance of the battery. Therefore, the formation of a stable SEI film is critical to the performance of a battery, and in the process of forming the SEI film, the SEI film formed by large-current formation is loose, and the SEI film formed by small-current formation is compact. The negative plate has the problem of lithium precipitation under the condition of high-current charging, so that the negative plate can not be used for lithium precipitation in the pre-charging process. It would be greatly advantageous to improve the production efficiency of a battery if the precharge time could be shortened without affecting the degree of densification of the SEI film and without the occurrence of the problem of lithium precipitation. The conventional lithium battery pre-charging method is usually a constant-current pre-charging mode, a constant-current equalizing charging mode, a constant-voltage drop current charging mode and a constant-current trickle charging mode, and the pre-charging process of the battery is completed by changing parameters of current and voltage in the pre-charging process by combining the pre-charging methods. The invention discloses a precharge method of a lithium ion battery, which is characterized in that the lithium ion battery is obtained by combining the steps of constant-current charging, constant-voltage charging, constant-current discharging and the like. The method comprises the steps of pre-formation and main formation, adopts low-pressure trickle segmentation formation in the formation stage of the SEI film at the front section, prevents the co-intercalation of lithium ions, increases the growth time of compact components of the SEI film, and forms a compact SEI film on the surface of the cathode material. The invention patent with the application number 201410621731.8 as a lithium battery pack charging method discloses a lithium battery pack charging method, which comprises four stages of small-current constant-current precharge, large-current constant-current balanced charge, constant-voltage-drop current mode and constant-current trickle charge, wherein the difference of battery cells is gradually reduced through the four stages, and the difference of the battery cells is reduced through prolonging the charging time in the whole charging process, so that the effects of more full battery charging and longer service life of the battery pack are achieved. The charging method can improve the consistency of the performances of the single batteries in the battery pack and prolong the service life of the batteries, but the charging time is longer in the charging process, which is not beneficial to improving the production efficiency of the batteries. In the battery production process, it is an important direction to improve the battery production efficiency by shortening the battery pre-charge time while ensuring the product performance. Disclosure of Invention In order to solve the defects in the prior art, the invention provides a lithium battery pre-charging method. Firstly, constant current charging is carried out on a battery until the voltage