Lithium/carbon monofluoride (Li/CFx) electrochemical cell projection model

• US 7,068,036 B1
• Filed: 10/28/2004
• Issued: 06/27/2006
• Est. Priority Date: 10/28/2003
• Status: Expired due to Fees

• Current Assignee: Greatbatch Limited (Greatbatch Incorporated)
• Original Assignee: Wiwilson Greatbatch Technologies Incorporated
• Inventors: Syracuse, Kenneth C., Takeuchi, Esther S.
• Primary Examiner(s): TIBBITS, PIA FLORENCE
• Application Number:
  US10/975,894
• Time in Patent Office: 607 Days
• Field of Search: 324/427, 324/426, 320/118, 320/136, 702/63, 429/50, 429/60, 429/91, 429/92, 429/231.7, 429/231.95, 429/245
• US Class Current: 324/427
• CPC Class Codes: H01M 10/42 Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells H01M10/60 takes precedence
• CPC Class Codes: H01M 10/4285 Testing apparatus
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H01M 4/5835 Comprising fluorine or fluoride salts
• CPC Class Codes: H01M 6/50 Methods or arrangements for servicing or maintenance, e.g. for maintaining operating temperature 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 6/5083 Testing apparatus
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A model for estimating the discharge profile of a Li/CF_x cell is described. The model uses as inputs the load at which the cell is subjected to and the planar surface area to estimate current density. Then, current density is used to estimate cell voltage at each 2% depth-of-discharge.

Claims

1. A method for estimating the voltage profile for an electrochemical cell, comprising the steps of:

a) providing electrochemical cell having an anode comprising lithium and a cathode comprising CF_x as a cathode active material activated with a nonaqueous electrolyte;

b) determining a planar interface area for the cell;

c) discharging the cell under a known load;

d) estimating a current density from a relationship between the known load and the planar interface area at a specified depth-of-discharge (DoD) using a first equation of;

current density=exp^{(a+b(ln(load))+c(PIA))};

e) calculating a relationship between the current density and a voltage using a second equation of;

voltage=d+e(current_density)³+f(ln(current_density)²); and

f) combining the current density and the voltage to predict a voltage capacity at the specified depth-of-discharge.

2. The method of claim 1 including determining a change in the planar interface area from a first DoD to a second, later DoD.

3. The method of claim 1 including specifying the depth-of-discharge from 0% to 100% DoD.

4. The method of claim 1 including deriving the coefficients a, b and c for the first equation from a range of the discharging known loads and planar interface area readings at each 2% DoD for the cell.

5. The method of claim 3 wherein the discharging known loads readings ranged from 4.53 kΩ

to 140 kΩ and

the planar interface area readings ranged from 9.88 cm² to 13.59 cm².

6. The method of claim 3 including selecting the coefficients a, b and c from Table 1.

7. The method of claim 1 including deriving the coefficients d, e and f for the second equation from a range of the discharging known loads and planar interface area readings at each 2% DoD for the cell.

8. The method of claim 7 including selecting the coefficients d, e and f from Table 2.

9. The method of claim 1 wherein the predicted voltage capacity at the specified DoD is applicable for a Li/CF_x cell the discharging known loads ranging from ±

25% of 4.53 kΩ

to 140 kΩ

.

10. The method of claim 1 wherein the predicted voltage capacity at the specified DoD is applicable for a Li/CF_x cell having a planar interface area ranging from ±

25% 9.88 cm² to 13.59 cm².

11. The method of claim 1 including providing the anode comprising a lithium alloy.

12. The method of claim 1 including providing the cathode comprising a fluoro-resin binder.

13. The method of claim 1 including providing the cathode comprising a conductive diluent.

14. The method of claim 1 including providing the cathode active material supported on a current collector selected from the group consisting of nickel, titanium, platinum, stainless steel, and gold.

15. The method of claim 1 including providing the cathode active material supported on a titanium current collector having a graphite/carbon coating thereon.

16. The method of claim 1 including providing the electrolyte comprising a lithium salt selected from the group consisting of LiPF₆, LiBF₄, LiAsF₆, LiSbF₆, LiClO₄, LiO₂, LiAlCl₄, LiGaCl₄, LiC(SO₂CF₃)₃, LiN(SO₂CF₃)₂, LiSCN, LiO₃SCF₃, LiC₆F₅SO₃, LiO₂CCF₃, LiSO₆F, LiB(C₆H₅)₄, LiCF₃SO₃, and mixtures thereof.

17. The method of claim 1 including providing the electrolyte comprising at least one solvent selected from the group consisting of tetrahydrofuran, methyl acetate, diglyme, trigylme, tetragylme, dimethyl carbonate, 1,2-dimethoxyethane, diethyl carbonate, propylene carbonate, ethylene carbonate, acetonitrile, dimethyl sulfoxide, dimethyl formamide, dimethyl acetamide, γ

-valerolactone, γ

-butyrolactone, N-methyl-pyrrolidinone, and mixtures thereof.

18. The method of claim 1 including providing the electrolyte comprising 1.0 M to 1.4 M LiBF₄ in γ

-butyrolactone.

19. The method of claim 1 including using the Li/CF_x cell to power an implantable medical device.

20. A method for estimating the voltage profile for an electrochemical cell, comprising the steps of:

a) providing electrochemical cell having an anode comprising lithium and a cathode comprising CF_x as a cathode active material activated with a nonaqueous electrolyte;

b) determining a planar interface area for the cell;

c) discharging the cell under a known load;

d) estimating a current density from a relationship between the known load and the planar interface area at a specified depth-of-discharge (DoD) using a first equation of;

current density=exp^{(a+b(ln(load))+c(PIA))};

e) calculating a relationship between the current density a and voltage using a second equation of;

voltage=d+e(current_density)³+f(ln(current_density)²);

f) combining the current density and the voltage to predict a voltage capacity at the specified depth-of-discharge; and

g) repeating steps b to f for a second DoD with the planar interface area having changed to thereby predict a second voltage capacity at the second DoD.