# US 2014/0197805 A1 · Diffusion-limited adaptive battery charging

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- Number: US 2014/0197805 A1
- Document ID: US20140197805A1
- Status: Published application
- Kind: A1
- Application number: 14/202,918
- Filed: 2014-03-10
- Published: 2014-07-17
- Earliest claimed: 2008-04-11
- Assignees: Apple Inc.
- Applicants: Apple Inc.
- Inventors: Thomas C. Greening; P. Jeffrey Ungar; William C. Athas
- Web page: https://patentgrep.com/patent/US20140197805A1

## CPC

- H01M 10/0525: Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
- H01M 10/44: Methods for charging or discharging (circuits for charging H02J7/00)
- H01M 10/443: {in response to temperature}
- 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)
- 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
- H02J 7/70: characterised by the mechanical construction
- H02J 7/90: Regulation of charging or discharging current or voltage
- G01P 3/56: for comparing two speeds
- G01P 15/00: Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- H01M 2300/00: Electrolytes
- H02J 7/00: Circuit arrangements for charging or discharging batteries or for supplying loads from batteries
- Y02E 60/10: Energy storage using batteries
- Y02T 10/70: Energy storage systems for electromobility, e.g. batteries
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- G01P: MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT (measuring or recording blood flow A61B5/02, A61B8/06; monitoring speed or deceleration of electrically-propelled vehicles B60L3/00; vehicle lighting systems adapted to indicate speed B60Q1/54; determining position or course in navigation, measuring ground distance in geodesy or surveying G01C; combined measuring devices for measuring two or more variables of movement G01C23/00; measuring velocity of sound G01H; measuring velocity of light G01J7/00; measuring direction or velocity of solid objects by reception or emission of radiowaves or other waves and based on propagation effects, e.g. Doppler effect, propagation time, direction of propagation, G01S; measuring speed of nuclear radiation G01T; measuring acceleration of gravity G01V; {measuring or recording the speed of trains B61L23/00; speed indicators incorporated in motor vehicles B60K35/00; measuring frequency or phase G01R; traffic control G08G})
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## 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

### Claim 1

A method for adaptively charging a battery, wherein the battery is a lithium-ion battery that 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 a charging current or a charging voltage based on the measured open circuit voltages; and
applying the calculated charging current or the calculated charging voltage to the battery.

### Claim 2 (depends on 1)

The method of claim 1, wherein calculating the charging current or the charging voltage based on the measured open circuit voltages includes:
calculating a 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; and
calculating the charging current or the charging voltage for the battery based on the calculated lithium surface concentration.

### Claim 3 (depends on 1)

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.

### Claim 4 (depends on 3)

The method of claim 3,
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.

### Claim 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 a charging current or a charging voltage based on the measured open circuit voltages, and
apply the charging current or the charging voltage to the battery.

### Claim 6 (depends on 5)

The lithium-ion battery of claim 5, wherein while calculating the charging current or the charging voltage, the controller is configured to:
calculate a 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; and
calculate the charging current or the charging voltage for the battery based on the calculated lithium surface concentration.

### Claim 7 (depends on 5)

The lithium-ion battery of claim 5,
wherein the transport-limiting electrode is a negative electrode; and
wherein the non-transport-limiting electrode is a positive electrode.

### Claim 8 (depends on 7)

The lithium-ion battery of claim 7,
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.

### Claim 9

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 a charging current or a charging voltage based on the measured open circuit voltages; and
applying the charging current or the charging voltage to the battery.

### Claim 10 (depends on 9)

The non-transitory computer-readable storage medium of claim 9, wherein calculating the charging current or the charging voltage based on the measured open circuit voltages includes:
calculating a 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; and
calculating the charging current or the charging voltage for the battery based on the calculated lithium surface concentration.

### Claim 11

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:
determining 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;
calculating a charging current or a charging voltage for the battery based on the determined lithium surface concentration; and
applying the charging current or the charging voltage to the battery.

### Claim 12 (depends on 11)

The method of claim 11, wherein the charging current or charging voltage is calculated to maintain the lithium surface concentration within set limits.

### Claim 13 (depends on 11)

The method of claim 11, wherein calculating the charging current or charging voltage involves maximizing the charging current or charging voltage while maintaining the lithium surface concentration within the set limits.

### Claim 14 (depends on 11)

The method of claim 11, wherein determining the lithium surface concentration involves:
measuring a diffusion time τ for lithium in the transport-limiting electrode; and
estimating the lithium surface concentration between τ measurements based on the diffusion time τ, a cell capacity Qmax for the battery and a measured charging current I for the battery.

### Claim 15 (depends on 14)

The method of claim 14, wherein measuring the diffusion time τ involves periodically:
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.

### Claim 16 (depends on 15)

The method of claim 15,
wherein the transport-limiting electrode is a negative electrode; and
wherein the non-transport-limiting electrode is a positive electrode.

### Claim 17 (depends on 16)

The method of claim 16,
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.