DETECTION METHOD OF LI PLATING, METHOD AND APPARATUS FOR CHARGING SECONDARY BATTERY AND SECONDARY BATTERY SYSTEM USING THE SAME

• US 20170234930A1
• Filed: 06/20/2016
• Published: 08/17/2017
• Est. Priority Date: 08/24/2015
• Status: Active Grant

• Current Assignee: LG Energy Solution Limited (LG Corporation)
• Original Assignee: LG Chem Limited (LG Corporation)
• Inventors: LEE, Hyeok-Moo, KIM, Hyo-Mi, LEE, Sol-Nip, OH, Song-Taek
• Granted Patent: US 10,126,367 B2
• Time in Patent Office: Days
• CPC Class Codes: G01N 27/02 by investigating impedance
• CPC Class Codes: G01R 31/36 Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: G01R 31/44 Testing lamps
• 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 10/48 Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

Provided is a non-destructive method for detecting lithium plating by which lithium plating can be detected in real time in an actual use environment of a secondary battery, a secondary battery charging method and apparatus for charging a secondary battery under the condition in which lithium plating does not occur by using this method, and a secondary battery system for detecting the state of a secondary battery by using this method. The method for detecting lithium plating according to the present disclosure is a method which detects lithium plating in a negative electrode in real time by observing a change in battery voltage as a function of SOC during charging a secondary battery, and determines a point at which a rise speed of the battery voltage slows down as a lithium plating occurrence point.

Claims

1. A method for detecting lithium plating, by which lithium plating in a negative electrode is detected in real time by observing a change in battery voltage as a function of SOC during charging a secondary battery, the method comprising:

determining a point at which a rise speed of the battery voltage slows down as a lithium plating occurrence point.

2. The method for detecting lithium plating according to claim 1, wherein the method comprises:

obtaining a SOC-V graph by measuring battery voltage as a function of SOC while charging the secondary battery;

obtaining a SOC-dV/dQ graph showing a change in battery voltage dV/dQ as a function of SOC from the SOC-V graph; and

determining a point at which a slope increase slows down on the SOC-dV/dQ graph as the lithium plating occurrence point.

3. A method for charging a secondary battery, comprising:

acquiring data by measuring battery voltage as a function of SOC at different charge rates;

obtaining a protocol designed to change a charge rate stepwise by setting a point at which a rise speed of the battery voltage slows down as a lithium plating occurrence point and charging limitation from the acquired data; and

charging a secondary battery according to the protocol.

4. The method for charging a secondary battery according to claim 3, wherein the charge rate at the data acquisition step is in a range of 0.25 C˜

5 C.

5. The method for charging a secondary battery according to claim 3, wherein the protocol has an initial charge rate higher than 1 C.

6. The method for charging a secondary battery according to claim 3, wherein the protocol has an initial charge rate of from 1.5 C to 5 C.

7. The method for charging a secondary battery according to claim 3, wherein the protocol includes a stepwise-decreasing charge rate and charge voltage information after termination of charging at each charge rate.

8. An apparatus for charging a secondary battery, comprising:

a power source unit configured to output charge voltage inputted from a commercial power source; and

a charging unit configured to output the charge voltage inputted from the power source unit to a secondary battery as a charge current, to charge the secondary battery, and when battery voltage of the secondary battery reaches a preset stage, to take control of the charge current to cause the charge current outputted to the secondary battery to change stepwise,

wherein the charging unit charges the secondary battery with the stepwise-adjusted charge current according to a protocol designed to change a charge rate stepwise by setting a point at which a rise speed of the battery voltage of the secondary battery slows down as a lithium plating occurrence point and charging limitation.

9. A secondary battery system, comprising a secondary battery,

the secondary battery system comprising:

a dV/dQ calculation means configured to calculate a value of dV/dQ, the value of dV/dQ being a ratio of a variation dQ of an amount of stored energy Q to a variation dV of battery voltage V of the secondary battery when the amount of stored energy Q in the secondary battery changed during charging of the secondary battery,

wherein a point at which a slope increase slows down on a SOC-dV/dQ graph showing a relationship between SOC and dV/dQ is determined as a lithium plating occurrence point in a negative electrode of the secondary battery.

10. The secondary battery system according to claim 9, wherein the secondary battery system comprises:

a current sensor to sense a current value I flowing in the secondary battery;

a voltage sensor to sense battery voltage of the secondary battery; and

a controller as the dV/dQ calculation means, and

the controller estimates an amount of stored energy in the secondary battery by integrating the current value for each predetermined time, obtains the battery voltage for each predetermined time by synchronizing with the integrated current, and calculates a value of dV/dQ by differentiating the battery voltage of the secondary battery with respect to its corresponding amount of stored energy during charging of the secondary battery.

11. The secondary battery system according to claim 9, wherein the controller stops charging when determining as the lithium plating occurrence point.

12. The secondary battery system according to claim 9, wherein the controller reduces at least one of charge current and charge voltage to the secondary battery while being charged, to accomplish full charge, when determining as the lithium plating occurrence point.