Abstract: The remaining capacity of a storage cell, particularly a valve regulated lead-acid cell, is determined by measuring its impedance at typically two or three relatively low frequencies f, e.g., frequencies in the approximate range of 0.001 to 1.0 Hz. In one application, the imaginary part Z" of the complex impedance Z(=Z'+jZ") is plotted vs. f.sup.-1/2, whereby the intercept Z".sub.o (at f.sup.-1/2 =0) of the bestfitting straight line of the plot is a measure of the cell's remaining capacity. In another application, the slope (dZ"/dZ') of a plot of the imaginary part Z" vs. real part Z' of the complex impedance Z, again as measured at relatively low frequencies f, is a measure of the cell's remaining capacity.

Abstract: This invention relates to a process of fabricating a rechargeable non-aqueous cell and to a cell produced by the process. The cell includes a unique laminated cathode structure. Other structural features of the non-aqueous cell including anode, non-aqueous electrolyte and separator, are generally conventional. The novel cathode is composed of a current collector consisting of an unperforated metal foil to which are bonded mats of cathode active material, selected from transition-metal chalcogenides. In the process of forming the cathode, a non-perforated metal foil, such as aluminum, is coated with a layer of bonding polymer and after the mats of cathode-active material, such as niobium triselenide, are placed on both sides of the metal foil, the composite is compacted, preferably by passing between rollers. Electronic conduction is enhanced by either admixing carbon black with the polymer or coating that surface of the mats which is to be in contact with the metal foil, with a thin layer of carbon black.

Abstract: A process of making a lithium cell with a positive electrode that comprises a niobium chalcogenide (e.g., NbSe.sub.3) active material. The process comprises forming the active material by a procedure that comprises forming a layer of Nb powder on an inert substrate (e.g., an alumina plate), and reacting the powder with selenium or sulfur vapor such that the desired (fibrous) chalcogenide is formed. The powder layer typically is formed by depositing (e.g., by spraying) a layer of slurry on the substrate, with the slurry comprising a liquid such as propylene glycol and Nb powder, and removing the liquid from the deposited slurry. The resulting layer of Nb powder can be of uniform thickness, advantageously is less than 0.1 mm thick, and adheres relatively well to the substrate. In preferred embodiments reacting the Nb powder with Se vapor comprises a two-stage heat treatment, the first stage comprising maintaining the powder in contact with Se vapor for at least four hours at a temperature in the range 520.