Preparation Of Epsilon-Phase Silver Vanadium Oxide From Gamma-Phase SVO Starting Material
The current invention relates to the preparation of an improved cathode active material for non-aqueous lithium electrochemical cell. In particular, the cathode active material comprises ε-phase silver vanadium oxide prepared by using a γ-phase silver vanadium oxide starting material. The reaction of γ-phase SVO with a silver salt produces the novel ε-phase SVO possessing a lower surface area than ε-phase SVO produces from vanadium oxide (V 2 O 5 ) and a similar silver salt as starting materials. Consequently, the low surface area ε-phase SVO material provides an advantage in greater long-term stability in pulse dischargeable cells.
1 . A cathode for an electrochemical cell, the cathode comprising an ε-phase silver vanadium oxide characterized as prepared from a mixture of γ-phase silver vanadium oxide having the formula Ag 1.2 V 3 O 8.1 and a metal salt to form a reaction mixture heated to at least one reaction temperature in an oxidizing atmosphere to produce the ε-phase silver vanadium oxide having the formula Ag 2 V 4 O 11 , wherein the metal salt is selected from one of:
Ag 2 O and the ε-phase silver vanadium oxide has a BET surface area of about 0.54 m 2 /gram, and
Ag 2 CO 3 and the ε-phase silver vanadium oxide has a BET surface area of about 0.44 m 2 /gram.
2 . The cathode of claim 1 wherein the reaction mixture is heated to the at least one reaction temperature in a range from about 300° C. to about 550° C.
3 . The cathode of claim 1 wherein the reaction mixture is heated to the at least one reaction temperature for about 5 hours to about 30 hours.
4 . The cathode of claim 1 further comprising a binder and a conductive material.
5 . A nonaqueous electrochemical cell, comprising:
a) an anode;
b) a cathode containing an electrode active material characterized as having been prepared from a mixture of γ-phase silver vanadium oxide having the formula Ag 1.2 V 3 O 8.1 and a metal salt forming a reaction mixture heated to at least one reaction temperature in an oxidizing atmosphere to produce the electrode active material selected from one of:
i) Ag 2 V 4 O 11 having a BET surface area of about 0.54 m 2 /gram with the metal salt having been Ag 2 O; and
ii) Ag 2 V 4 O 11 having a BET surface area of about 0.44 m 2 /gram with the metal salt having been Ag 2 CO 3 ; and
c) a non-aqueous electrolyte activating the anode and the cathode; and
d) a separator material electrically insulating the anode from the cathode, and of a porosity to allow for electrolyte flow.
6 . The electrochemical cell of claim 5 wherein the anode is comprised of lithium.
7 . The electrochemical cell of claim 5 wherein the reaction mixture is heated to the at least one reaction temperature in a range from about 300° C. to about 550° C.
8 . The electrochemical cell of claim 5 wherein the reaction mixture is heated to the at least one reaction temperature for about 5 hours to about 30 hours.
9 . A cathode for an electrochemical cell, the cathode comprising an electrode active material characterized as prepared from γ-phase silver vanadium oxide having the formula Ag 1.2 V 3 O 8.1 mixed with a metal salt compound to form a reaction mixture heated to at least one reaction temperature in an oxidizing atmosphere to produce the electrode active material selected from the group consisting of Mn 0.2 Ag 0.8 V 2 O 5.8 , and Mg 0.2 Ag 0.8 V 2 O 5.6 .
10 . The cathode of claim 9 wherein the metal salt is selected from the group consisting of manganese carbonate, manganese oxide, magnesium carbonate, magnesium oxide, and combinations and mixtures thereof.