Diffusion-limited adaptive battery charging

• US 8,754,611 B2
• Filed: 09/30/2008
• Issued: 06/17/2014
• Est. Priority Date: 04/11/2008
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Greening, Thomas C., Ungar, P. Jeffrey, Athas, William C.
• Primary Examiner(s): Assouad, Patrick
• Assistant Examiner(s): BROWN, LAMARR A
• Application Number:
  US12/242,641
• Publication Number:
  US 20090256528A1
• Time in Patent Office: 2,086 Days
• Field of Search: 320146-147, 320/112, 320/113, 320/134, 320/156, 429/221, 429/231.3, 429/231.5, 429/61
• US Class Current: 320/112
• CPC Class Codes: G01P 15/00 Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
• CPC Class Codes: G01P 3/56 for comparing two speeds
• 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 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H01M 10/443 in response to temperature
• 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 2300/00 Electrolytes
• CPC Class Codes: H01M 50/00 Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
• CPC Class Codes: H02J 7/0042 characterised by the mechanical construction
• CPC Class Codes: H02J 7/007 Regulation of charging or discharging current or voltage
• 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

Some embodiments of the present invention provide a system that adaptively charges a battery, wherein the battery is a lithium-ion battery which includes a transport-limiting electrode governed by diffusion, an electrolyte separator and a non-transport-limiting electrode. During operation, the system determines a lithium surface concentration at an interface between the transport-limiting electrode and the electrolyte separator based on a diffusion time for lithium in the transport-limiting electrode. Next, the system calculates a charging current or a charging voltage for the battery based on the determined lithium surface concentration. Finally, the system applies the charging current or the charging voltage to the battery.

Claims

1. A method for adaptively charging a battery, wherein the battery is a lithium-ion battery which includes a transport-limiting electrode governed by diffusion, an electrolyte separator and a non-transport-limiting electrode, comprising while the battery is charging:

charging the battery with a fixed current for a fixed time period;

entering a zero current state in which the charging current is set to zero;

during the zero current state, measuring an open circuit voltage for the battery at two times while the open circuit voltage relaxes toward a steady state; and

calculating the diffusion time τ

based on the measured open circuit voltages;

calculating a lithium surface concentration based on the diffusion time τ

, a state of charge of the battery q and a temperature of the battery T;

calculating a charging current or a charging voltage for the battery based on the calculated lithium surface concentration; and

applying the charging current or the charging voltage to the battery.

2. The method of claim 1,

wherein the transport-limiting electrode is a negative electrode;

and

wherein the non-transport-limiting electrode is a positive electrode.

3. The method of claim 2,

wherein the negative electrode is comprised of graphite and/or TiS₂;

wherein the electrolyte separator is a liquid electrolyte comprised of LiPF₆, LiBF₄ and/or LiClO₄ and an organic solvent; and

wherein the positive electrode is comprised of LiCoO₂, LiMnO₂, LiFePO₄ and/or Li₂FePO₄F.

4. An adaptive charging mechanism for a battery, wherein the battery is a lithium-ion battery which includes a transport-limiting electrode governed by diffusion, an electrolyte separator and a non-transport-limiting electrode, comprising:

a current sensor configured to measure a charging current for the battery;

a voltage sensor configured to measure a voltage across terminals of the battery;

a charging source configured to apply a charging current or a charging voltage to the battery;

a controller configured to receive inputs from the current sensor and the voltage sensor and configured to send a control signal to the charging source;

wherein, while the battery is charging, the controller is configured to;

charge the battery with a fixed current for a fixed time period,

enter a zero current state in which the charging current is set to zero,

during the zero current state, measure an open circuit voltage for the battery at two times while the open circuit voltage relaxes toward a steady state, and

calculate the diffusion time τ

based on the measured open circuit voltages,

calculate a lithium surface concentration based on the diffusion time τ

, a state of charge of the battery q and a temperature of the battery T,

calculate a charging current or a charging voltage for the battery based on the calculated lithium surface concentration, and

apply the charging current or the charging voltage to the battery.

5. A lithium-ion battery with an adaptive charging mechanism, comprising:

a transport-limiting electrode governed by diffusion;

an electrolyte separator;

a non-transport-limiting electrode;

a current sensor configured to measure a charging current for the battery;

a voltage sensor configured to measure a voltage across terminals of the battery;

a charging source configured to apply a charging current or a charging voltage to the battery;

a controller configured to receive inputs from the current sensor and the voltage sensor, and configured to send a control signal to the charging source;

wherein, while the battery is charging, the controller is configured to;

charge the battery with a fixed current for a fixed time period,

enter a zero current state in which the charging current is set to zero,

during the zero current state, measure an open circuit voltage for the battery at two times while the open circuit voltage relaxes toward a steady state, and

calculate the diffusion time τ

based on the measured open circuit voltages,

calculate a lithium surface concentration based on the diffusion time τ

, a state of charge of the battery q and a temperature of the battery T,

calculate a charging current or a charging voltage for the battery based on the calculated lithium surface concentration, and

apply the charging current or the charging voltage to the battery.

6. The battery of claim 5,

wherein the transport-limiting electrode is a negative electrode;

and

wherein the non-transport-limiting electrode is a positive electrode.

7. The battery of claim 6,

wherein the negative is comprised of graphite and/or TiS₂;

wherein the electrolyte separator is a liquid electrolyte comprised of LiPF₆, LiBF₄ and/or LiClO₄ and an organic solvent; and

wherein the positive electrode is comprised of LiCoO₂, LiMnO₂, LiFePO₄ and/or Li₂FePO₄F.

8. A non-transitory computer-readable storage medium storing instructions that when executed by a controller for a battery cause the controller to perform a method for adaptively charging a battery, wherein the battery is a lithium-ion battery which includes a transport-limiting electrode governed by diffusion, an electrolyte separator and a non-transport-limiting electrode, the method comprising while the battery is charging:

charging the battery with a fixed current for a fixed time period;

entering a zero current state in which the charging current is set to zero;

during the zero current state, measuring an open circuit voltage for the battery at two times while the open circuit voltage relaxes toward a steady state; and

calculating the diffusion time τ

based on the measured open circuit voltages;

calculating a lithium surface concentration based on the diffusion time τ

, a state of charge of the battery q and a temperature of the battery T;

calculating a charging current or a charging voltage for the battery based on the calculated lithium surface concentration; and

applying the charging current or the charging voltage to the battery.