Chemistry: electrical current producing apparatus – product – and – Process of cell operation
Reexamination Certificate
2001-11-08
2004-05-04
Ruthkosky, Mark (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Process of cell operation
C429S220000, C429S231950
Reexamination Certificate
active
06730429
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to methods of operating intermetallic negative electrodes for non-aqueous lithium cells and batteries. More specifically, it relates to methods of operating modified compositions of copper-tin electrodes, Cu
6-x
M
x
Sn
5
, wherein x≦3 and in which M is one or more metals including silicon, and to methods using current collectors and grain growth inhibitors when used with such electrodes, and to controlled operating conditions for the lithium cells and batteries using such intermetallic electrodes. Preferred compositions useful in the inventive methods include Cu
6-x
M
x
Sn
5
electrodes in which the copper atoms are partially replaced by one or more transition metals and lithium in partial replacement M and Li or one or more of M including Li. Improved electrochemical performance with respect to delivered capacity and cycling stability of the lithium cells over those known in the art is obtained by controlling the structure of the lithiated Cu
6-x
M
x
Sn
5
electrodes and by controlling the voltage of the lithium cell such that the potential of the lithiated intermetallic negative electrode at the top of charge is less than 0.2 V but greater than 0 V vs. metallic lithium.
A significant problem in the field is that copper-tin electrodes, notably Cu
6
Sn
5
, lose capacity if cycled repeatedly to 0 V vs. metallic lithium. When cycled to 200 mV vs. lithium, the capacity retention is improved significantly, but at the expense of the delivered amount of capacity.
SUMMARY OF THE INVENTION
The invention relates to a method of using intermetallic negative electrodes based on copper-tin, Cu
6
Sn
5
, for non-aqueous electrochemical lithium cells and batteries. The invention relates more specifically to the use of modified electrode compositions, Cu
6-x
M
x
Sn
5
, wherein x≦3 and where M is one or more metals used in the inventive method, preferably a first row transition metal and lithium, that when cycled in an electrochemical cell the voltage of cell is controlled such that the potential of the lithiated intermetallic negative electrode at the top of charge is less than 0.2 V but greater than 0 V vs. metallic lithium. The Cu
6-x
M
x
Sn
5
electrodes optionally contain additional M metal (or metals) in the electrode either in finely divided, dispersed and intimately mixed form or as a substrate to act as current collector. The electrodes may also contain additional components to control porosity and current collection or to suppress grain growth in the electrode during electrochemical operation. Such modifications to the composition of copper-tin electrodes and to the regulation of the operating conditions of the cells improve the capacity and cycle life of lithium cells and batteries. The superior electrochemical performance is achieved by controlling the structure of the lithiated Cu
6-x
M
x
Sn
5
electrodes, either electronically by controlling the voltage of the lithium cell, or by limiting the installed capacity in the positive electrode.
REFERENCES:
patent: 5770333 (1998-06-01), Saito et al.
patent: 6203944 (2001-03-01), Turner et al.
patent: 6528208 (2003-03-01), Thackeray et al.
patent: 2002/0064704 (2002-05-01), Thackeray et al.
patent: 2002/0136953 (2002-09-01), Vaughey et al.
patent: WO 00/03443 (2000-01-01), None
NiAs-versus zinc-blende-type intermetallic insertion electrodes for lithium batteries: lithium extraction from Li2CuSn; J.T. Vaughey, et al.; Electrochemistry Communications 1 (1999) 517-521.
Intermetallic insertion electrodes derived from NiAs-, Ni2In-, and Li2CuSn-type structures for lithium-ion batteries; M.M. Thackeray, et al.; Electrochemistry Communications 1 (1999) 111-115.
In SituX-Ray Study of the Electrochemical Reaction of Li with &eegr;'—Cu6Sn5; D. Larcher, et al.; Journal of The Electrochemical Society, 147 (5) (2000) 1658-1662.
LixCu6Sn5(0<x<13) : An Intermetallic Insertion Electrode for Rechargeable Lithium Batteries; Keith D. Kepler, et al; Electro-chemical and Solid-State Letters, 2 (7) (1999) 307-309.
Intermetallic Insertion Electrodes for Lithium Batteries; J. T. Vaughey, et al.; Electrochemical Society Proceedings, vol. 99-24 280-289.
Copper-tin anodes for rechargeable lithium batteries: an example of the matrix effect in an intermetallic system; K.D. Kepler, et al.; Journal of Power Sources 81-82 (1999) 383-387.
Lithium storage properties of nanocrystalline eta-Cu6Sn5alloys prepared by ball-milling; G.X. Wang, et al.; Journal of Alloys and Compounds 299 (2000) L12-L15.
Science and Applications of Mixed Conductors for Lithium Batteries; Michael M. Thackeray, et al., MRS Bulletin, Mar. 2000, 39-46.
Edstrom Ester Kristina
Fransson Linda M. L.
Henriksen Gary
Johnson Christopher S.
Thackeray Michael M.
Emrich and Dithmar
Ruthkosky Mark
The University of Chicago
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