Rechargeable battery cell with improved high temperature performance
An alkaline, rechargeable electrochemical cell includes a pasted electrode structure in which a composition comprising a paste matrix component includes cobalt in an amount greater than 6 weight percent ranging up to 14 weight percent. The matrix may also include a rare earth such as yttrium. The composition further includes particles of nickel hydroxide dispersed in the matrix, and these particles include cobalt levels ranging from greater than 8 atomic percent up to 15 atomic percent. Cells incorporating these materials have good charging efficiency at elevated temperatures.
1. A positive electrode composition for use in an alkaline, rechargeable electrochemical cell, said composition comprising:
a matrix material comprising a mixture of nickel hydroxide and a cobalt material comprising cobalt metal and/or a cobalt oxide, and/or cobalt hydroxide, wherein the weight percent of cobalt in said mixture relative to the nickel component thereof is greater than 6% and less than or equal to 14%; and
particles of nickel hydroxide dispersed in said matrix, said nickel hydroxide particles being doped in their bulk with cobalt, the atomic percent of said cobalt being greater than 8% and less than or equal to 12%, said nickel hydroxide particles also having a coating of cobalt oxyhydroxide disposed thereupon.
2. The electrode composition of claim 1 , wherein the weight percent of cobalt in said matrix is in the range of 8% to 12%.
3. The electrode composition of claim 1 , wherein said matrix includes a binder.
4. The electrode composition of claim 1 , wherein said matrix comprises a paste.
5. The electrode composition of claim 1 , wherein said particles of nickel hydroxide are comprised of a plurality of microcrystallites having a particle size of less than 100 angstroms, based on the reflection peak from the <101> plane.
6. The electrode composition of claim 5 , wherein said microcrystallites have a particle size of less than 90 angstroms based on the reflection peak from the <101> plane.
7. A positive electrode for use in an alkaline, rechargeable electrochemical cell, said electrode comprising a substrate having the electrode composition of claim 1 supported thereupon.
8. An alkaline, rechargeable electrochemical cell, said cell including the electrode of claim 7 .
9. A method of making an electrode for a rechargeable alkaline electrochemical cell, said method comprising the steps of:
providing a matrix material comprising a mixture of nickel hydroxide and a cobalt material, said cobalt material comprising cobalt and/or cobalt oxide, wherein the weight percent of cobalt in said mixture, relative to the nickel hydroxide component in said mixture, is greater than 6% percent and less than or equal to 14%;
providing particles of nickel hydroxide, said particles including a cobalt dopant wherein the atomic percent of said cobalt dopant is greater than 8% and less than or equal to 12%;
disposing said particles in said matrix so as to form an electrode composition;
providing a substrate; and
disposing said electrode composition on said substrate.
10. The method of claim 9 , wherein said matrix material comprises a paste and further includes a binder.
11. The method of claim 9 , wherein said matrix comprises a dry material.
12. The method of claim 9 , wherein said substrate is a foamed nickel substrate and wherein said electrode composition is at least partially disposed within the pores of said foam.
13. The method of claim 9 , including the further step of contacting said electrode with an electrolyte which comprises an aqueous solution of an alkali metal hydroxide.
14. The method of claim 13 , wherein the majority of the alkali metal hydroxide in said electrolyte is sodium hydroxide.
15. The method of claim 9 , wherein said particles of nickel hydroxide are comprise of a plurality of microcrystallites having a particle size of less than 100 angstroms based on the reflection peak from the <101> plane.
16. The method of claim 9 , wherein the particles of nickel hydroxide are substantially spherical and have an average diameter in the range of 5-20 microns.
17. A positive electrode composition for use in an alkaline, rechargeable electrochemical cell, said composition comprising:
a matrix material comprising a mixture of nickel hydroxide, a cobalt material comprising cobalt metal and/or a cobalt oxide, and a rare earth material, wherein the weight percent of cobalt in said mixture relative to the nickel component thereof is greater than 6% and less than or equal to 14%; and a rare earth material; and
particles of nickel hydroxide doped in their bulk with cobalt dispersed in said matrix, the atomic percent of said cobalt being greater than 8% and less than or equal to 12%, said nickel hydroxide particles having a coating of cobalt oxyhydroxide disposed thereupon.
18. The positive electrode composition of claim 17 , wherein said rare earth material comprises yttrium and/or yttrium oxide.
19. The positive electrode composition of claim 18 , wherein the amount of yttrium in said rare earth material is in the range of 0.5 to 5 weight percent.
20. The positive electrode composition of claim 18 , wherein the amount of yttrium in said rare earth material is in the range of 0.5 to 2 weight percent.