EP-4737925-A1 - BATTERY DIAGNOSTIC DEVICE AND METHOD

EP4737925A1EP 4737925 A1EP4737925 A1EP 4737925A1EP-4737925-A1

Abstract

An apparatus for diagnosing a battery according to the present disclosure includes a capacity calculating unit configured to calculate a positive electrode capacity value and a negative electrode capacity value of the battery, respectively, for each predetermined number of charge and discharge cycles; a degradation rate calculating unit configured to calculate a positive electrode degradation rate and a negative electrode degradation rate of the battery, respectively, based on the positive electrode capacity values and the negative electrode capacity values calculated by the capacity calculating unit; and a diagnosing unit configured to diagnose a state of the battery by referring to a comparison result of comparing the positive electrode degradation rate and the negative electrode degradation rate.

Inventors

SONG, HEE-SEOK
KIM, YONG-JUN
BAE, YOON-JUNG

Assignees

LG Energy Solution, Ltd.

Dates

Publication Date: 20260506
Application Date: 20240902

Claims (15)

An apparatus for diagnosing a battery, which diagnoses a state of a battery capable of repeated charging and discharging, the apparatus for diagnosing a battery comprising: a capacity calculating unit configured to calculate a positive electrode capacity value and a negative electrode capacity value of the battery, respectively, for each predetermined number of charge and discharge cycles; a degradation rate calculating unit configured to calculate a positive electrode degradation rate and a negative electrode degradation rate of the battery, respectively, based on the positive electrode capacity values and the negative electrode capacity values calculated by the capacity calculating unit; and a diagnosing unit configured to diagnose a state of the battery by referring to a comparison result of comparing the positive electrode degradation rate and the negative electrode degradation rate.
The apparatus for diagnosing a battery according to claim 1, wherein the capacity calculating unit is configured to generate a battery profile representing a correspondence relationship between capacity and voltage of the battery that changes while the battery is being charged or discharged, before calculating the positive electrode capacity value and the negative electrode capacity value, and to calculate the positive electrode capacity value and the negative electrode capacity value, respectively, based on the battery profile.
The apparatus for diagnosing a battery according to claim 2, wherein the capacity calculating unit is configured to generate a first differential profile representing a correspondence relationship between a differential capacity, which is obtained by differentiating the capacity of the battery with respect to the voltage of the battery, and the voltage of the battery, based on the battery profile, and to calculate the positive electrode capacity value using the first differential profile.
The apparatus for diagnosing a battery according to claim 3, wherein the capacity calculating unit is configured to select a partial section from an entire section of the first differential profile, calculate an area between a voltage axis representing the voltage of the first differential profile and the partial section, and calculate the positive electrode capacity value based on the calculated area.
The apparatus for diagnosing a battery according to claim 2, wherein the capacity calculating unit is configured to generate a second differential profile representing a correspondence relationship between a differential voltage, which is obtained by differentiating the voltage of the battery with respect to the capacity of the battery, and the capacity of the battery, based on the battery profile, and to calculate the negative electrode capacity value using the second differential profile.
The apparatus for diagnosing a battery according to claim 5, wherein the capacity calculating unit is configured to select two peaks among peaks appearing in the second differential profile according to a predetermined selection criterion, calculate a capacity difference between the two peaks, and calculate the negative electrode capacity value based on the calculated capacity difference.
The apparatus for diagnosing a battery according to claim 1, wherein the degradation rate calculating unit is configured to calculate the positive electrode degradation rate and the negative electrode degradation rate based on a positive electrode capacity decrease amount and a negative electrode capacity decrease amount of the battery that are generated at each charge and discharge cycle of the battery.
The apparatus for diagnosing a battery according to claim 1, further comprising: a NP ratio calculating unit for calculating a NP ratio of the battery by using the positive electrode capacity value and the negative electrode capacity value of the battery calculated at a diagnosis point of the battery, wherein the diagnosing unit is configured to determine the state of the battery by further referring to a comparison result of comparing the NP ratio with a predetermined reference NP ratio.
The apparatus for diagnosing a battery according to claim 8, wherein the diagnosing unit is configured to diagnose the state of the battery as a normal state that does not require a change in a charge condition or a discharge condition of the battery, when the NP ratio is not smaller than the reference NP ratio and the negative electrode degradation rate is not faster than the positive electrode degradation rate.
The apparatus for diagnosing a battery according to claim 8, wherein the diagnosing unit is configured to diagnose the state of the battery as a first abnormal state that requires a change in a charge condition or a discharge condition of the battery, when the NP ratio is not smaller than the reference NP ratio, but the negative electrode degradation rate is faster than the positive electrode degradation rate.
The apparatus for diagnosing a battery according to claim 8, wherein the diagnosing unit is configured to diagnose the state of the battery as a second abnormal state that requires discontinuation of use of the battery, when the NP ratio is smaller than the reference NP ratio.
The apparatus for diagnosing a battery according to claim 1, wherein the diagnosing unit is configured to diagnose the state of the battery as an abnormal state that requires a change in a charge condition or a discharge condition of the battery or discontinuation of use, when the negative electrode degradation rate is faster than the positive electrode degradation rate, and wherein the apparatus for diagnosing a battery further comprises a charge and discharge adjusting unit configured to change the charge condition or the discharge condition of the battery or to stop charging and discharging of the battery, when the state of the battery is diagnosed as an abnormal state.
A battery pack comprising the apparatus for diagnosing a battery according to any one of claims 1 to 12.
A vehicle comprising the apparatus for diagnosing a battery according to any one of claims 1 to 12.
A method performed by a processor for diagnosing a battery capable of repeated charging and discharging, the method comprising: calculating a positive electrode capacity value and a negative electrode capacity value of the battery, respectively, for each predetermined number of charge and discharge cycles; calculating a positive electrode degradation rate and a negative electrode degradation rate of the battery based on the positive electrode capacity values and the negative electrode capacity values calculated; and diagnosing a state of the battery by referring to a comparison result of comparing the positive electrode degradation rate and the negative electrode degradation rate.

Description

TECHNICAL FIELD This application is based on and claims priority from Korean Patent Application No. 10-2023-0136849, filed on October 13, 2023, with the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. The present disclosure relates to an apparatus and method for diagnosing a battery, and more particularly, to an apparatus and method for diagnosing a state of a battery capable of repeated charging and discharging. BACKGROUND ART Recently, the demand for portable electronic products such as notebook computers, digital cameras and portable telephones has increased sharply, and electric vehicles, energy storage systems, robots, satellites and the like have been developed in earnest. Accordingly, high-performance batteries allowing repeated charging and discharging are being actively studied. Types of rechargeable batteries include lithium batteries that use lithium ions, such as lithium-ion batteries or lithium-ion polymer batteries, and nickel cadmium batteries, nickel hydrogen batteries, and nickel zinc batteries. Among these, lithium batteries have the advantages of having a relatively long lifespan, a very low self-discharge rate, and high energy density because they have almost no memory effect compared to batteries that use nickel, and thus their application range is gradually expanding. Meanwhile, the positive electrode and negative electrode of such a battery gradually degrade as the number of charge and discharge cycles of the battery increases, resulting in a decrease in electrical capacity. In this case, the positive electrode and negative electrode may degrade at different rates. The difference in degradation rate between the positive electrode and negative electrode may result in rapid performance degradation, shortened lifespan, or damage to the separator of the battery. For example, in the case of a lithium battery, if the degradation rate of the negative electrode is faster than the degradation rate of the positive electrode so that the capacity of the negative electrode decreases below the capacity of the positive electrode, the lithium ions of the positive electrode are converted into lithium metal through a side reaction with the electrolyte and deposited on the surface of the negative electrode, which causes a lithium plating phenomenon. This lithium plating phenomenon further reduces the capacity of the negative electrode, shortens the life of the battery, and may damage the separator between the positive electrode and the negative electrode, resulting in battery failure or thermal runaway. Therefore, a battery diagnostic technology is required that may accurately determine the point in time when a change in charge and discharge condition applied to the battery is required by monitoring the battery degradation rate for each electrode. However, as disclosed in Japanese Patent Laid-Open Publication No. 2009-252381, since the existing technology determines the degradation state of a battery on a battery-by-battery basis through differential voltage analysis, there is a problem in that the degradation rate of each electrode of the battery cannot be confirmed, and as a result, the point in time when a change in charge and discharge condition applied to the battery is required cannot be accurately determined. DISCLOSURE Technical Problem The technical challenge that the present disclosure seeks to solve is to provide an apparatus and method for diagnosing a battery that may prevent performance degradation and shortened lifespan of the battery by monitoring the degradation rate of the battery for each electrode. Another technical challenge that the present disclosure seeks to solve is to provide an apparatus and method for diagnosing a battery that may extend the life of the battery while ensuring the safety of the battery. Another technical challenge that the present disclosure seeks to solve is to provide a battery pack and a vehicle including the apparatus for diagnosing a battery according to the present disclosure. Technical Solution An apparatus for diagnosing a battery according to one aspect of the present disclosure diagnoses a state of a battery capable of repeated charging and discharging, and comprises a capacity calculating unit configured to calculate a positive electrode capacity value and a negative electrode capacity value of the battery, respectively, for each predetermined number of charge and discharge cycles; a degradation rate calculating unit configured to calculate a positive electrode degradation rate and a negative electrode degradation rate of the battery, respectively, based on the positive electrode capacity values and the negative electrode capacity values calculated by the capacity calculating unit; and a diagnosing unit configured to diagnose a state of the battery by referring to a comparison result of comparing the positive electrode degradation rate and the negative electrode degradation rate. In a