BATTERY MODULE AND ASSEMBLED BATTERY

• US 20160254687A1
• Filed: 12/01/2014
• Published: 09/01/2016
• Est. Priority Date: 11/29/2013
• Status: Active Grant

• Current Assignee: Vehicle Energy Japan, Inc.
• Original Assignee: Hitachi Automotive Systems Limited (Hitachi, Ltd.)
• Inventors: TANAKA, Akihide, YAGI, Yohshin
• Granted Patent: US 10,063,072 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B60L 2240/545 Temperature
• CPC Class Codes: B60L 2240/547 Voltage
• CPC Class Codes: B60L 2240/549 Current
• CPC Class Codes: B60L 50/51 characterised by AC-motors
• CPC Class Codes: B60L 50/64 Constructional details of batteries specially adapted for electric vehicles
• CPC Class Codes: B60L 58/15 Preventing overcharging
• CPC Class Codes: B60L 58/20 having different nominal voltages
• CPC Class Codes: B60L 58/21 having the same nominal voltage
• 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 10/425 Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing printed circuits H05K1/00
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H01M 10/46 Accumulators structurally combined with charging apparatus 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: H01M 2004/027 Negative electrodes
• CPC Class Codes: H01M 2010/4271 Battery management systems including electronic circuits, e.g. control of current or voltage to keep battery in healthy state, cell balancing
• CPC Class Codes: H01M 2220/20 Batteries in motive systems, e.g. vehicle, ship, plane
• CPC Class Codes: H01M 4/386 Silicon or alloys based on silicon
• CPC Class Codes: H01M 4/587 for inserting or intercalating light metals
• CPC Class Codes: H01M 4/625 Carbon or graphite
• CPC Class Codes: H02J 2310/48 for electric vehicles [EV] or hybrid vehicles [HEV]
• CPC Class Codes: H02J 7/00302 : Overcharge protection
• CPC Class Codes: H02J 7/00306 : Overdischarge protection
• CPC Class Codes: H02J 7/007182 : in response to battery voltage
• CPC Class Codes: H02J 7/04 : Regulation of charging current or voltage
• CPC Class Codes: H02J 7/1415 : with a generator driven by a prime mover other than the motor of a vehicle
• CPC Class Codes: H02J 7/1492 : by means of controlling devices between the generator output and the battery
• CPC Class Codes: Y02E 60/10 : Energy storage using batteries
• CPC Class Codes: Y02T 10/70 : Energy storage systems for electromobility, e.g. batteries

Abstract

A battery module includes a lithium ion secondary battery and a control circuit. The control circuit includes a measurement unit which measures voltage, current, and the time of charge/discharge of the lithium ion secondary battery; an operation unit which calculates a capacity based on the voltage, the current, and the time and calculates a differential value dQ/dV by differentiating the capacity with a voltage; a threshold voltage setting unit which specifies a peak of a low capacity side of the differential value dQ/dV generated on the basis of a stage structure of graphite and sets a voltage at the peak to a threshold voltage; a cutoff voltage setting unit which sets a discharge cutoff voltage of the lithium ion secondary battery on the basis of the threshold voltage; and a charge/discharge control unit which controls charge/discharge of the lithium ion secondary battery on the basis of the discharge cutoff voltage.

Claims

1. A battery module, comprising:

a lithium ion secondary battery which has a negative electrode mixture layer including a silicon-based active material and graphite on a surface of a negative electrode; and

a control circuit which controls charge/discharge of the lithium ion secondary battery,

wherein the control circuit includes

a measurement unit which measures a voltage, a current, and a time of the charge/discharge of the lithium ion secondary battery,

an operation unit which calculates a capacity Q of the lithium ion secondary battery on the basis of the voltage, the current, and the time and calculates a differential value dQ/dV by differentiating the capacity Q with the voltage V,

a threshold voltage setting unit which specifies a peak of a low capacity side of the differential value dQ/dV generated on the basis of a stage structure of the graphite and sets a voltage at the peak to a threshold voltage,

a cutoff voltage setting unit which sets a discharge cutoff voltage of the lithium ion secondary battery on the basis of the threshold voltage, and

a charge/discharge control unit which controls the charge/discharge of the lithium ion secondary battery on the basis of the discharge cutoff voltage.

2. The battery module according to claim 1, wherein

the control circuit includes a storage unit in which a maximum value of a capacity difference of the capacity at the threshold voltage and the capacity at the discharge cutoff voltage is previously recorded,

the operation unit calculates the capacity difference on the basis of a measurement result of the measurement unit, and

the cutoff voltage setting unit sets the discharge cutoff voltage to a voltage corresponding to a capacity obtained by subtracting the maximum value from the capacity at the threshold voltage, when the calculated capacity difference is larger than the recorded maximum value.

3. The battery module according to claim 2, wherein the maximum value is equal to or smaller than 20% of a capacity based on the silicon-based active material.

4. The battery module according to claim 3, wherein the silicon-based active material is silicon oxide and when a sum of mass of the silicon oxide and the graphite included in the negative electrode mixture layer is set to 100 wt %, the negative electrode mixture layer includes the silicon oxide at a ratio of 2 wt % to 65 wt %.

5. The battery module according to claim 4, wherein the negative electrode mixture layer includes the silicon oxide at a ratio of 10 wt % or less.

6. A battery pack, comprising:

the battery module according to any one of claims 1 to 5; and

a plurality of lithium ion secondary batteries.

7. The battery pack according to claim 6, further comprising:

cell controllers each of which controls each of the lithium ion secondary batteries,

wherein the charge/discharge control unit is provided in each of the cell controllers.