US-12625192-B2 - Device, system, and method for performance estimation of rechargeable battery

US12625192B2US 12625192 B2US12625192 B2US 12625192B2US-12625192-B2

Abstract

Discussed are a device, a system and a method for estimating a performance of a rechargeable battery. The device can include a current sensor to measure a discharge current output from a rechargeable battery during a discharge period in which the rechargeable battery is discharged from a predetermined reference voltage with a constant voltage, and a control circuit to calculate a resistance change relationship depending on a State of Charge (SOC) change during the discharge period based on the predetermined reference voltage and a change of the discharge current depending on time passage.

Inventors

Ji Hye PARK
Wontae JOE

Assignees

LG ENERGY SOLUTION, LTD.

Dates

Publication Date: 20260512
Application Date: 20210727
Priority Date: 20200929

Claims (15)

1 . A device for estimating a performance of a rechargeable battery for use as a fully assembled rechargeable battery, the device comprising: a current sensor to measure a discharge current output from the rechargeable battery during a discharge period in which the rechargeable battery is discharged from a predetermined reference voltage with a constant voltage; and a control circuit to: calculate a resistance change relationship depending on a State of Charge (SOC) change during the discharge period based on the predetermined reference voltage and a change of the discharge current depending on time passage, and generate a resistance value of each of a first resistance as a resistance due to a voltage drop of the rechargeable battery, a second resistance as a resistance generated as an ion is inserted into an active material of the rechargeable battery during the discharge period, and a third resistance as a polarization resistance generated by a movement of the ion in the rechargeable battery, based on the resistance change relationship according to the SOC change of the discharge period, verify that the rechargeable battery is usable as the fully assembled rechargeable battery based on the performance of the rechargeable battery during the discharge period by comparing the polarization resistance with a reference value to determine whether the polarization resistance is less than or more than the reference value, select the rechargeable battery as passing a performance index that is expected from the fully assembled rechargeable battery when the polarization resistance is less than the reference value, select the rechargeable battery as failing the performance index that is expected from the fully assemble rechargeable battery when the polarization resistance is more than the reference value, and control a discharger to discharge the rechargeable battery with a predetermined constant current to lower a voltage of the rechargeable battery to correspond to the predetermined reference voltage, wherein the polarization resistance corresponding to the performance index expected from the fully assembled rechargeable battery is calculated as the reference value.
2 . The device of claim 1 , wherein the control circuit, in the resistance change relationship depending on the SOC change during the discharge period, uses a resistance value of a starting point of the discharge period as the resistance value for the first resistance, calculates a resistance value at an end point of the discharge period as an upper limit value of the second resistance on an extending line connecting a first point corresponding to the resistance value of the discharge period and a second point where a resistance change ratio for the SOC change exceeds a first reference value in the resistance change relationship for the SOC change, and calculates the resistance value of the second resistance based on a difference of the upper limit value of the second resistance and the resistance value of the first resistance.
3 . The device of claim 2 , wherein the control circuit calculates the resistance value of the third resistance based on a difference of the resistance value of the end point of the discharge period and the upper limit value of the second resistance.
4 . The device of claim 3 , wherein the control circuit compares the resistance value of the third resistance with a second reference value to determine an output performance of the rechargeable battery.
5 . The device of claim 1 , further comprising a voltage sensor to measure a voltage of the rechargeable battery to be transmitted to the control circuit.
6 . The device of claim 1 , wherein, when the rechargeable battery is continuously discharged, the control circuit further uses the polarization resistance as an index for predicting an output performance at a discharge end time of the rechargeable battery.
7 . The device of claim 1 , wherein the polarization resistance of the rechargeable battery is inversely proportional to a porosity of a positive electrode of the rechargeable battery and is proportional to a porosity of a negative electrode of the rechargeable battery.
8 . The device of claim 1 , wherein the rechargeable battery passing the performance index is selected for use in an electric device that includes at least one of vehicles (EVs) and energy storage systems (ESSs).
9 . A system for estimating a performance of a rechargeable battery for use as a fully assembled rechargeable battery, the system comprising: a discharger to discharge the rechargeable battery from a predetermined reference voltage with a constant voltage; a current sensor to measure a discharge current output from the rechargeable battery during a discharge period during which the rechargeable battery is discharged; and a control circuit to: calculate a resistance change relationship depending on a State of Charge (SOC) change during the discharge period based on the predetermined reference voltage and a change of the discharge current depending on time passage, and generate a resistance value of each of a first resistance as a resistance due to a voltage drop of the rechargeable battery, a second resistance as a resistance generated as an ion is inserted into an active material of the rechargeable battery during the discharge period, and a third resistance as a polarization resistance generated by a movement of the ion in the rechargeable battery, based on the resistance change relationship according to the SOC change of the discharge period, verify that the rechargeable battery is usable as the fully assembled rechargeable battery based on the performance of the rechargeable battery during the discharge period by comparing the polarization resistance with a reference value to determine whether the polarization resistance is less than or more than the reference value, select the rechargeable battery as passing a performance index that is expected from the fully assembled rechargeable battery when the polarization resistance is less than the reference value, and select the rechargeable battery as failing the performance index that is expected from the fully assemble rechargeable battery when the polarization resistance is more than the reference value, wherein the polarization resistance corresponding to the performance index expected from the fully assembled rechargeable battery is calculated as the reference value, and wherein the discharger discharges the rechargeable battery with a predetermined constant current under a control of the control circuit to lower a voltage of the rechargeable battery to correspond to the predetermined reference voltage.
10 . The system of claim 9 , wherein the control circuit, in the resistance change relationship depending on the SOC change during the discharge period, uses a resistance value of a starting point of the discharge period as the resistance value for the first resistance, calculates a resistance value at an end point of the discharge period as an upper limit value of the second resistance on an extending line connecting a first point corresponding to the resistance value of the discharge period and a second point where a resistance change ratio for the SOC change exceeds a first reference value in the resistance change relationship for the SOC change, and calculates the resistance value of the second resistance based on a difference of the upper limit value of the second resistance and the resistance value of the first resistance.
11 . The system of claim 10 , wherein the control circuit calculates the resistance value of the third resistance based on a difference of the resistance value of the end point of the discharge period and the upper limit value of the second resistance.
12 . The system of claim 9 , wherein, when the rechargeable battery is continuously discharged, the control circuit further uses the polarization resistance as an index for predicting an output performance at a discharge end time of the rechargeable battery.
13 . A method for estimating a performance of a rechargeable battery for use as a fully assembled rechargeable battery, the method comprising: controlling, by a control circuit, a rechargeable battery to be discharged from a predetermined reference voltage with a constant voltage; receiving, by the control circuit, a measuring value of a discharge current output from the rechargeable battery during a discharge period in which the rechargeable battery is discharged; calculating, by the control circuit, a resistance change relationship depending on a State of Charge (SOC) change during the discharge period based on the predetermined reference voltage and a change of the discharge current according to time passage and generating a resistance value of each a first resistance as a resistance due to a voltage drop of the rechargeable battery, a second resistance as a resistance generated as an ion is inserted in an active material of the rechargeable battery during the discharge period, and a third resistance as a polarization resistance generated by a movement of the ion in the rechargeable battery, based on the resistance change relationship depending on the SOC change during the discharge period; verifying, by the control circuit, that the rechargeable battery is usable as the fully assembled rechargeable battery based on the performance of the rechargeable battery during the discharge period by comparing the polarization resistance with a reference value to determine whether the polarization resistance is less than or more than the reference value, selecting, by the control circuit, the rechargeable battery as passing a performance index that is expected from the fully assembled rechargeable battery when the polarization resistance is less than the reference value; selecting, by the control circuit, the rechargeable battery as failing the performance index that is expected from the fully assemble rechargeable battery when the polarization resistance is more than the reference value; and discharging, by a discharger under a control of the control circuit, the rechargeable battery with a predetermined constant current to lower a voltage of the rechargeable battery to correspond to the predetermined reference voltage, wherein the polarization resistance corresponding to the performance index expected from the fully assembled rechargeable battery is calculated as the reference value.
14 . The method of claim 13 , wherein the calculating of the resistance value includes: calculating, by the control circuit, a resistance value of a starting point of the discharge period as the resistance value for the first resistance; calculating, by the control circuit, the resistance value at an end point of the discharge period as an upper limit value of the second resistance and calculating the resistance value of the second resistance based on a difference of the upper limit value of the second resistance and the resistance value of the first resistance on an extending line connecting a first point corresponding to the resistance value of the starting point of the discharge period and a second point where a resistance change ratio for the SOC change exceeds a first reference value based on the resistance change relationship for the SOC change; and calculating, by the control circuit, the resistance value of the third resistance based on a resistance value of the end point of the discharge period and the upper limit value of the second resistance.
15 . The method of claim 13 , further comprising: using, by the control circuit, the polarization resistance as an index for predicting an output performance at a discharge end time of the rechargeable battery when the rechargeable battery is continuously discharged.

Description

CROSS-REFERENCE TO RELATED APPLICATION Technical Field This application claims priority to and the benefit of Korean Patent Application No. 10-2020-0126848 filed in the Korean Intellectual Property Office on Sep. 29, 2020, the entire contents of which are incorporated herein by reference. The present invention relates to a device, a system, and a method for estimating performance of a rechargeable battery. Background Art As a demand for lithium rechargeable batteries changes from small portable electronic devices to medium and large electric vehicles (EVs) and energy storage systems (ESSs), the required battery characteristics are also significantly changing. As well as significantly strengthened requirements such as a long-term reliability of more than 10 years, safety of a pack level, and price competitiveness security compared to existing small batteries, a high power characteristic and fast charging performance are also required. Recently, there have been attempts to improve output by improving a movement speed of electrons or improving a movement speed of ions. For example, there are various attempts such as research on technology to increase conductivity to improve the movement speed of the electrons, or adding new materials to improve the movement speed of the ions (Li+). What is required, accompanying this, is a method of measuring or estimating how much output of the rechargeable battery has improved by improving the movement speed of the electrons or the ions (Li+). However, in order to measure output of the rechargeable battery, since the voltage and the current must be simultaneously measured and controlled, it is much more difficult than measuring the capacity of a conventional unit battery cell. In addition, it has been pointed out as a problem because the measured value tends to vary greatly depending on the measurement conditions such as an output holding time, a state-of-charge (SOC), a cut-off condition, and a measurement temperature, as well as the selection of the method for measuring the output of the rechargeable battery. Therefore, there is a need for a method that can easily and accurately estimate how much the output performance or the rapid charging performance of the rechargeable battery has improved due to the improvement of the movement speed of the ions. DISCLOSURE Technical Problem The present invention provides a device, a system, and a method for a performance estimation of a rechargeable battery for estimating the output improvement of the rechargeable battery according to the improvement of the movement speed of the ion based on a polarization resistance (Rpola), which is a resistance caused by the movement of the ions. The present invention provides a device, a system, and a method for a performance estimation of a rechargeable battery for discharging the rechargeable battery with a constant current (CC) mode and a constant voltage (CV) mode and quantifying the polarization resistance (Rpola) based on the discharge current output from the rechargeable battery in the constant voltage (CV) mode. The present invention provides a device, a system, and a method for a performance estimation of a rechargeable battery for determining that the rechargeable battery to be verified exceeds a predetermined output performance if the polarization resistance (Rpola) value is less than a predetermined reference value. Technical Method A device of the present invention includes: a current sensor to measure a discharge current output from a rechargeable battery during a discharge period in which the rechargeable battery is discharged from a predetermined reference voltage with a constant voltage; and a control circuit to calculate a resistance change relationship depending on a State of Charge (SOC) change during the discharge period based on the predetermined reference voltage and a change of the discharge current depending on time passage, wherein the control unit calculates a resistance value of each of a first resistance as a resistance due to a voltage drop of the rechargeable battery, a second resistance as a resistance generated as an ion is inserted into an active material of the rechargeable battery during the discharge period, and a third resistance as a polarization resistance generated by a movement of the ion in the rechargeable battery, based on the resistance change relationship according to the SOC change of the discharge period. The control unit, in a resistance change relationship depending on the SOC change during the discharge period, may use a resistance value of a starting point of the discharge period as a resistance value for the first resistance, calculate a resistance value at an end point of the discharge period as an upper limit value of the second resistance on an extending line connecting a first point corresponding to the resistance value of the discharge period and a second point where a resistance change ratio for the SOC change exceeds a first reference val