Constant-current charging and discharging method for lithium secondary battery by controlling current based on internal resistance measurement

Patent metadata

Field	Value
Publication number	US-10734688-B2
Application number	US-201715405359-A
Country	US
Kind code	B2
Filing date	Jan 13, 2017
Priority date	Jan 19, 2016
Publication date	Aug 4, 2020
Grant date	Aug 4, 2020

Abstract

A charging and discharging method for a lithium secondary battery is provided, wherein, while charging or discharging the lithium secondary battery using a constant current, the charge current or allowable discharge current is modified by measuring the internal resistance of the lithium secondary battery. In the charging and discharging method for a lithium secondary battery according to the present disclosure, the charging time and charge capacity, or the discharge current amount and discharge capacity, may be appropriately harmonized, and thus the method may be usefully used as a charging method and a discharging method for a lithium secondary battery.

First claim

What is claimed is:

1. A charging method for a lithium secondary battery, the charging method comprising:
(1) charging the lithium secondary battery by applying a constant current for a first time period to provide an applied voltage, said lithium secondary battery have an open-circuit voltage where the constant current is cut off;
(2) measuring an internal resistance in order to determine a measured internal resistance by a method of cutting off the constant current and measuring the open-circuit voltage for a second time period and comparing the applied voltage to the open-circuit voltage;
(3) modifying the value of the constant current to a modified constant current value used for charging according to the measured internal resistance value;
(4) charging the lithium secondary battery by applying the modified constant current value for a third time period; and (5) sequentially repeating operations (2) to (4);
wherein each of operations (1) and (4) is performed during the first and third time periods 10 ms to 100 seconds,
wherein in operation (2) the measuring of the internal resistance by the method of cutting off the constant current and measuring the open-circuit voltage is performed during the second time period of 8 ms to 8 seconds,
wherein the internal resistance is the resistance of a negative electrode comprised in the lithium secondary battery.

2. The charging method of claim 1 , wherein the constant current value, modified in operation (3) according to the measured internal resistance value, is adjusted so as to be inversely proportional to the measured internal resistance.

3. The charging method of claim 1 , wherein, when operations (2) to (4) are sequentially repeated, when the internal resistance value measured in operation (2) increases, the constant current is decreased in operation (3).

4. The charging method of claim 3 , wherein, when the measured internal resistance value increases by 1%, the constant current value decreases by 0.1 to 10%.

5. The charging method of claim 1 , wherein, when operations (2) to (4) are sequentially repeated, when the internal resistance value measured in operation (2) decreases, the constant current is increased in operation (3).

6. The charging method of claim 5 , wherein, when the measured internal resistance decreases by 1%, the constant current value increases by 0.1 to 10%.

7. A discharging method for a lithium secondary battery having an open-circuit voltage, the discharging method comprising:
(1) discharging the lithium secondary battery for a first time period using a predetermined discharge current value to provide a predetermined voltage;
(2) measuring an internal resistance in order to determine a measured internal resistance value by a method of cutting off the predetermined discharge current and measuring the open-circuit voltage in a second time period and comparing the predetermined voltage to the open-circuit voltage of the lithium secondary battery when the predetermined discharge current value is cut off;
(3) modifying the predetermined discharge current value to a modified discharge current value according to the measured internal resistance value;
(4) discharging the lithium secondary battery for a third time period within the modified discharge current value, and
(5) subsequently repeating operations (2) to (4);
wherein each of operations (1) and (4) is performed during the first and third time periods of 10 ms to 100 seconds,
wherein in operation (2) the measuring of the internal resistance by the method of cutting off the constant current and measuring the open-circuit voltage is performed during the second time period of 8 ms to 8 seconds,
wherein the internal resistance is the resistance of a negative electrode comprised in the lithium secondary battery.

8. The discharging method of claim 7 , wherein the allowable discharge current value modified in operation (3) according to the measured internal resistance value is adjusted so as to be inversely proportional to the measured internal resistance value.

9. The discharging method of claim 7 , wherein, when operations (2) to (4) are sequentially repeated, when the internal resistance value measured in operation (2) increases, the allowable discharge current is decreased in operation (3).

10. The discharging method of claim 9 , wherein, when the measured internal resistance value increases by 1%, the allowable discharge current value decreases by 0.1 to 10%.

11. The discharging method of claim 7 , wherein, when operations (2) to (4) are sequentially repeated, when the internal resistance value measured in operation (2) decreases, the allowable discharge current is increased in operation (3).

12. The discharging method of claim 11 , wherein, when the measured internal resistance value decreases by 1%, the allowable discharge current value increases by 0.1 to 10%.

Assignees

• Lg Chemical Ltd

Inventors

• Chae Oh Byong
• Lee Su Min
• Kim Eun Kyung
• Shin Sun Young

Classifications

• H02J7/965

  obtained with the battery disconnected from the charge or discharge circuit · CPC title

• H02J7/855

  with circuits adapted for supplying loads from the battery · CPC title

• H02J7/585

  Sequential battery discharge in systems with a plurality of batteries · CPC title

• H02J7/50

  acting upon multiple batteries simultaneously or sequentially · CPC title

• Y02E60/10

  Energy storage using batteries · CPC title