Charging control method for lithium-ion battery, charging control apparatus for lithium-ion battery and lithium-ion battery system

• US 9,882,406 B2
• Filed: 08/18/2015
• Issued: 01/30/2018
• Est. Priority Date: 09/04/2014
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Satou, Yoshinori, Uchiyama, Masaki, Yamamoto, Nobuo, Ohira, Koji
• Primary Examiner(s): Tso, Edward
• Assistant Examiner(s): Omar, Ahmed
• Application Number:
  US14/828,727
• Publication Number:
  US 20160072313A1
• Time in Patent Office: 896 Days
• Field of Search: 320162
• CPC Class Codes: H01M 10/0525 Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H01M 10/46 Accumulators structurally combined with charging apparatus circuits for charging H02J7/00
• CPC Class Codes: H02J 7/007 Regulation of charging or discharging current or voltage
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A lithium-ion battery includes a cathode active material of the Olivine-type crystal structure. The lithium-ion battery is charged under control of a charging control apparatus, which performs a charging process for charging up to a target voltage according to a constant-current and constant-voltage charging method, a negative-electrode potential evaluation process for evaluating a potential change quantity at the negative-electrode, and a voltage setting process for setting the target voltage to a lower voltage based on the potential change quantity of the negative-electrode evaluated by the negative-electrode potential evaluation process. The charging voltage is changed from the target voltage to the set voltage even when the negative-electrode potential changes with an increase in the number of charging and aging deterioration. Thus a positive-electrode potential is suppressed from rising because of less susceptibility to the increase in number of charging and aging deterioration.

Claims

1. A charging control method for controlling charging of a lithium-ion battery, which is provided with a positive electrode and a negative electrode, the charging control method comprising:

charging processing for charging the lithium-ion battery to a target voltage by a constant-current and constant-voltage charging method, the lithium-ion battery including a cathode active material having Olivine-type crystal structure;

negative-electrode potential evaluation processing for evaluating a potential change quantity of the negative electrode; and

voltage setting processing for setting the target voltage to decrease based on the potential change quantity of the negative-electrode evaluated by the negative-electrode potential evaluation processing;

wherein

the negative-electrode potential evaluation processing evaluates the potential change quantity of the negative-electrode based on one of or both of a charging voltage, which is measured as a voltage charged to the lithium-ion battery, and a discharging voltage, which is measured as a voltage discharged from the lithium-ion battery; and

the negative-electrode potential evaluation processing specifies a stepwise change point, at which a quantity of change in one of or both of the charging voltage and the discharging voltage relative to the charging rate changes in excess of a threshold value, and evaluates the potential change quantity of the negative electrode based on a shift quantity of the stepwise change point in increasing and decreasing directions.

2. The charging control method for controlling charging of a lithium-ion battery according to claim 1, wherein:

the negative-electrode potential evaluation processing evaluates the potential change quantity of the negative electrode based on a difference value between the charging voltage and the discharging voltage, which are at a same charging rate.

3. The charging control method for controlling charging of a lithium-ion battery according to claim 1, wherein:

the negative-electrode potential evaluation processing specifies the stepwise change point, with respect to a characteristic curve of one of or both of the charging voltage and the discharging voltage, based on a differentiation coefficient, which is calculated by differentiating the voltage by the charging rate.

4. A charging control apparatus for controlling charging of a lithium-ion battery, which is provided with a positive electrode and a negative electrode, the charging control apparatus comprising:

a charging part for charging the lithium-ion battery to a target voltage by a constant-current and constant-voltage charging method, the lithium-ion battery including a cathode active material having Olivine-type crystal structure;

a negative-electrode potential evaluation part for evaluating a potential change quantity of the negative electrode; and

voltage setting part for setting the target voltage to decrease based on the potential change quantity of the negative-electrode evaluated by the negative-electrode potential evaluation part;

wherein

the negative-electrode potential evaluation part evaluates the potential change quantity of the negative-electrode based on one of or both of a charging voltage, which is measured as a voltage charged to the lithium-ion battery, and a discharging voltage, which is measured as a voltage discharged from the lithium-ion battery; and

the negative-electrode potential evaluation part specifies a stepwise change point, at which a quantity of change in one of or both of the charging voltage and the discharging voltage relative to the charging rate changes in excess of a threshold value, and evaluates the potential change quantity of the negative electrode based on a shift quantity of the stepwise change point in increasing and decreasing directions.

5. The charging control method for controlling charging of a lithium-ion battery according to claim 4, wherein:

the negative-electrode potential evaluation part evaluates the potential change quantity of the negative electrode based on a difference value between the charging voltage and the discharging voltage, which are at a same charging rate.

6. The charging control method for controlling charging of a lithium-ion battery according to claim 4, wherein:

the negative-electrode potential evaluation part specifies the stepwise change point, with respect to a characteristic curve of one of or both of the charging voltage and the discharging voltage, based on a differentiation coefficient, which is calculated by differentiating the voltage by the charging rate.

7. A lithium-ion battery system comprising:

the charging control apparatus according to claim 4; and

the lithium battery.