Apparatus and method for testing performance of battery cell

Patent metadata

Field	Value
Publication number	US-2021156923-A1
Application number	US-201916613482-A
Country	US
Kind code	A1
Filing date	Jan 8, 2019
Priority date	Jan 9, 2018
Publication date	May 27, 2021
Grant date	—

Abstract

Provided is an apparatus and method for testing the electrochemical performance of a battery cell in a non-destructive manner. The apparatus includes a measuring unit configured to measure an open circuit voltage (OCV) of the battery cell, a memory unit configured to store data obtained through pre-experiments for each of a plurality of reference cells and a process deviation value occurred in a manufacturing process of the battery cell, and a control unit electrically connected to the measuring unit and the memory unit. The control unit is configured to determine at least one of a capacity of the battery cell, an estimated profile data indicating a change in OCV of the battery cell in a predetermined state of charge (SOC) range and a resistance of the battery cell.

First claim

1 . An apparatus for testing performance of a battery cell, comprising:
a measuring unit electrically connected to the battery cell, the measuring unit being configured to measure an open circuit voltage (OCV) of the battery cell with a change in state of charge (SOC) of the battery cell; a memory unit configured to store a plurality of profile data indicating a change in OCV of a positive electrode or a negative electrode of each of a plurality of reference cells, a plurality of upper limits corresponding to an amount of lithium ions stored in the positive electrode or the negative electrode of each of the plurality of reference cells at an upper limit of a predetermined SOC range, a plurality of lower limits corresponding to an amount of lithium ions stored in the positive electrode or the negative electrode of each of the plurality of reference cells at a lower limit of the predetermined SOC range, and a process deviation value occurred in a manufacturing process of the battery cell; and a control unit electrically connected to the measuring unit and the memory unit, the control unit being configured to:
generate a plurality of reference profile data indicating a change in OCV of the plurality of reference cells in the predetermined SOC range based on the plurality of profile data, the plurality of upper limits, and the plurality of lower limits;
generate measured profile data indicating a change in OCV of the battery cell in the predetermined SOC range; and
determine at least one of a capacity of the battery cell, an estimated profile data indicating a change in OCV of the battery cell in the predetermined SOC range, and a resistance of the battery cell based on the plurality of reference profile data, the measured profile data, and the process deviation value.

2 . The apparatus according to claim 1 , wherein the process deviation value includes at least one of a deviation value of an amount of positive electrode active materials per unit area, a deviation value of an amount of negative electrode active materials per unit area, a deviation value of a total positive electrode area, and a deviation value of a total negative electrode area, of the battery cell occurred in the manufacturing process of the battery cell.

3 . The apparatus according to claim 1 , wherein:
the plurality of profile data includes positive electrode profile data and negative electrode profile data of each of the plurality of reference cells; the plurality of upper limits includes a reference positive electrode upper limit and a reference negative electrode upper limit of each of the plurality of reference cells; the plurality of lower limits includes a reference positive electrode lower limit and a reference negative electrode lower limit of each of the plurality of reference cells; the positive electrode profile data indicates a change in OCV of the positive electrode of the reference cell with a change in an amount of lithium ions stored in the positive electrode of the reference cell; the negative electrode profile data indicates a change in OCV of the negative electrode of the reference cell with a change in an amount of lithium ions stored in the negative electrode of the reference cell; the reference positive electrode upper limit indicates an amount of lithium ions stored in the positive electrode of the reference cell at the upper limit of the predetermined SOC range; the reference negative electrode upper limit indicates an amount of lithium ions stored in the negative electrode of the reference cell at the upper limit of the predetermined SOC range; the reference positive electrode lower limit indicates an amount of lithium ions stored in the positive electrode of the reference cell at the lower limit of the predetermined SOC range; and the reference negative electrode lower limit indicates an amount of lithium ions stored in the negative electrode of the reference cell at the lower limit of the predetermined SOC range.

4 . The apparatus according to claim 2 , wherein:
the control unit is configured to determine an estimated positive electrode upper limit, an estimated positive electrode lower limit, an estimated negative electrode upper limit and an estimated negative electrode lower limit of the battery cell based on the plurality of reference profile data and the measured profile data; the estimated positive electrode upper limit indicates an amount of lithium ions stored in the positive electrode of the battery cell at the upper limit of the predetermined SOC range; the estimated positive electrode lower limit indicates an amount of lithium ions stored in the positive electrode of the battery cell at the lower limit of the predetermined SOC range; the estimated negative electrode upper limit indicates an amount of lithium ions stored in the negative electrode of the battery cell at the upper limit of the predetermined SOC range; and the estimated negative electrode lower limit indicates an amount of lithium ions stored in the negative electrode of the battery cell at the lower limit of the predetermined SOC range.

5 . The apparatus according to claim 4 , wherein the control unit is further configured to:
declare a cost function indicating a sum of squares of residuals between the plurality of reference profile data and the measured profile data; and estimate the estimated positive electrode upper limit, the estimated positive electrode lower limit, the estimated negative electrode upper limit, and the estimated negative electrode lower limit of the battery cell, such that a value of the cost function is minimum.

6 . The apparatus according to claim 5 , wherein:
the control unit is further configured to calculate a positive electrode irreversible capacity, a negative electrode irreversible capacity, and a negative electrode side reaction capacity of the battery cell based on the plurality of profile data, the estimated positive electrode upper limit, the estimated positive electrode lower limit, the estimated negative electrode upper limit, and the estimated negative electrode lower limit; the positive electrode irreversible capacity indicates an unusable capacity of the positive electrode of the battery cell outside the predetermined SOC range; the negative electrode irreversible capacity indicates an unusable capacity of the negative electrode of the battery cell outside the predetermined SOC range; and the negative electrode side reaction capacity indicates a side reaction capacity generated by a Solid Electrolyte Interface (SEI) film formed on a surface of the negative electrode of the battery cell.

7 . The apparatus according to claim 6 , wherein the control unit is further configured to determine the capacity of the battery cell using:
a positive electrode reversible capacity corresponding to a capacity range from the estimated positive electrode lower limit to the estimated positive electrode upper limit; a negative electrode reversible capacity corresponding to a capacity range from the estimated negative electrode lower limit to the estimated negative electrode upper limit; and the capacity of the battery cell being equal.

8 . The apparatus according to claim 6 , wherein the control unit is configured to determine the capacity of the battery cell, the estimated profile data, and the resistance of the battery cell based on the process deviation value and the negative electrode side reaction capacity.

9 . The apparatus according to claim 8 , wherein the control unit is configured to estimate the capacity of the battery cell by multiplying a capacity density constant corresponding to the negative electrode side reaction capacity by the process deviation value.

10 . A method for testing pe

Assignees

• Lg Chemical Ltd

Inventors

• Nam Gi-Min
• Lim Jin-Hyung
• Yoon Du-Seong
• Joe Won-Tae

Classifications

• G01R31/3842

  combining voltage and current measurements · CPC title

• G01R31/396

  Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery · CPC title

• G01R31/3835 Primary

  involving only voltage measurements · CPC title

• G01R31/392 Primary

  Determining battery ageing or deterioration, e.g. state of health · CPC title

• G01R31/389 Primary

  Measuring internal impedance, internal conductance or related variables · CPC title