Apparatus and method for estimating voltage of secondary battery including blended cathode material

• US 9,207,287 B2
• Filed: 08/22/2013
• Issued: 12/08/2015
• Est. Priority Date: 06/13/2012
• Status: Active Grant

• Current Assignee: LG Energy Solution Limited (LG Corporation)
• Original Assignee: LG Chem Limited (LG Corporation)
• Inventors: Joe, Won-Tae, Chung, Geun-Chang
• Primary Examiner(s): NGHIEM, MICHAEL P
• Application Number:
  US13/973,384
• Publication Number:
  US 20130338950A1
• Time in Patent Office: 838 Days
• Field of Search: 702/63
• US Class Current: 1/1
• CPC Class Codes: G01R 31/3644 Constructional arrangements
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/378 specially adapted for the type of battery or accumulator
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• CPC Class Codes: G01R 31/385 Arrangements for measuring battery or accumulator variables for monitoring G01R31/382
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables
• 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: H01M 4/13 Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
• CPC Class Codes: H01M 4/362 Composites
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

An apparatus for estimating a voltage of a secondary battery which includes a cathode including a first cathode material and a second cathode material with different activating voltage ranges, an anode including an anode material and a separator for separating the cathode from the anode. The apparatus includes a control unit configured to estimate a voltage of a secondary battery based on a circuit model including a first cathode material circuit, a second cathode material circuit and an anode material circuit, each circuit modeled to change its voltage according to a State Of Charge (SOC) of the electrode material corresponding the circuit and a current flowing through the circuit.

Claims

1. An apparatus for estimating a voltage of a secondary battery including first and second cathode materials, the apparatus comprising:

a voltage and current sensor unit configured to provide, when the secondary battery initiates charging or discharging, a measured operation initiating voltage of the second battery and, at time intervals during the charging or discharging of the secondary battery, a measured current of the secondary battery to the control unit; and

a control unit configured to estimate the voltage of the secondary battery during charging or discharging of the secondary battery based on a circuit model of the secondary battery, the circuit model including;

a first cathode material circuit modeled by adding a first open-circuit voltage according to a State of Charge (SOC) of the first cathode material and a first impedance voltage according to an impedance component of the first cathode material,

a second cathode material circuit connected to the first cathode material circuit in parallel and modeled by adding a second open-circuit voltage according to an SOC of a second cathode material and a second impedance voltage according to an impedance component of the second cathode material, and

an anode material circuit connected to the first and second cathode material circuits in series and modeled by adding a third open-circuit voltage according to an SOC of the anode material and a third impedance voltage according to an impedance component of the anode material,

wherein the control unit estimates the voltage of the secondary battery during charging or discharging of the secondary battery based on the circuit model and by using the measured operation initiating voltage and the measured current of the secondary battery, and controls the charging or discharging of the secondary battery by using the estimated voltage of the secondary battery.

2. The apparatus for estimating a voltage of a secondary battery according to claim 1, wherein the control unit calculates:

the open-circuit voltage according to the SOC of the first cathode material by using a look-up table or a look-up function by which the open-circuit voltage is defined in advance according to each SOC of the first cathode material;

the open-circuit voltage according to the SOC of the second cathode material by using a look-up table or a look-up function by which the open-circuit voltage is defined in advance according to each SOC of the second cathode material; and

the open-circuit voltage according to the SOC of the anode material by using a look-up table or a look-up function by which the open-circuit voltage is defined in advance according to each SOC of the anode material.

3. The apparatus for estimating a voltage of a secondary battery according to claim 1, wherein the control unit calculates:

the impedance voltage according to the impedance component of the first cathode material by using an impedance voltage calculation equation derived from a connection relation and an electrical characteristic value of a circuit element constituting the impedance component of the first cathode material and a current flowing through the first cathode material circuit;

the impedance voltage according to the impedance component of the second cathode material by using an impedance voltage calculation equation derived from a connection relation and an electrical characteristic value of a circuit element constituting the impedance component of the second cathode material and a current flowing through the second cathode material circuit; and

the impedance voltage according to the impedance component of the anode material by using an impedance voltage calculation equation derived from a connection relation and an electrical characteristic value of a circuit element of the impedance component of the anode material and a current flowing through the anode material circuit.

4. The apparatus for estimating a voltage of a secondary battery according to claim 3, wherein the control unit sets initial values of the impedance voltages formed by the impedance components of the first cathode material, the second cathode material and the anode material as 0 (zero).

5. The apparatus for estimating a voltage of a secondary battery according to claim 1, wherein the control unit sets initial values for the SOCs of the first cathode material, the second cathode material and the anode material by using the operation initiating voltage.

6. The apparatus for estimating a voltage of a secondary battery according to claim 5,

wherein the control unit sets initial values for the SOCs of the first cathode material, the second cathode material and the anode material, respectively, by using equations below:

z_c1[0]=OCV<sup>−

1</sup>_c1(V_cell[0]+OCV_a(OCV<sup>−

1</sup>_cell(V_cell[0])))

z_c2[0]=OCV<sup>−

1</sup>_c2(V_cell[0]+OCV_a(OCV<sup>−

1</sup>_cell[0])))

z_a[0]=z_cell[0]=OCV<sup>−

1</sup>_cell(V_cell[0])

wherein z_c1[0], z_c2[0] and z_a[0] respectively represent initial values for the SOCs of the first cathode material, the second cathode material and the anode material;

OCV_a represents an operator for transforming the SOC of the anode material into an open-circuit voltage formed at the anode material circuit;

OCV<sup>−

1</sup>_c1, OCV<sup>−

1</sup>_c2, and OCV<sup>−

1</sup>_cell are respectively inverse transformation operators of OCV_c1, OCV_c2 and OCV_cell, OCV_c1, OCV_c2 and OCV_cell are operators for transforming the SOCs of the first cathode material, the second cathode material and the secondary battery into open-circuit voltages formed at the first cathode material circuit, the second cathode material and the secondary battery, respectively, and V_cell[0] is the operation initiating voltage.

7. The apparatus for estimating a voltage of a secondary battery according to claim 1, wherein the impedance component of each circuit includes at least one circuit element selected from the group consisting of one or more resistance elements and one or more capacitor elements, and combinations thereof.

8. The apparatus for estimating a voltage of a secondary battery according to claim 1, wherein the impedance component of each circuit includes a plurality of circuit elements, and

wherein the plurality of circuit elements are connected in series and/or in parallel.

9. The apparatus for estimating a voltage of a secondary battery according to claim 1, further comprising a storage unit configured to store the estimated voltage of the secondary battery.

10. The apparatus for estimating a voltage of a secondary battery according to claim 1, further comprising a display unit configured to display the estimated voltage of the secondary battery.

11. The apparatus for estimating a voltage of a secondary battery according to claim 1, wherein the control unit outputs the estimated voltage of the secondary battery.

12. The apparatus for estimating a voltage of a secondary battery according to claim 1, wherein the apparatus is an electric-driven apparatus.