NOVELTY - An enhanced-performance rechargeable electrochemical energy storage cell (10) consists of a container (16), and positive electrode(s) (24), and negative electrode(s) (28). Application of an electric potential across the electrode connectors for electric current to flow, effects e.g. reduction of metal transfer within cell, reduction of gas evolution from treated cell, reduction in water consumption by treated cell, increase in on-charge potential of treated cell, and reduction in self-discharge of treated cell, when compared to performance of an untreated cell.    USE - Enhanced-performance rechargeable electrochemical energy storage cell (claimed). Uses include but are not limited to power sources of indoor and outdoor electric vehicles, telephone exchanges, residence, office and industrial equipment, computers, servers, load-leveling applications, and signaling and lighting applications.    ADVANTAGE - The enhanced-performance rechargeable electrochemical energy storage cell comprises a supplement which typically exhibits foaming of an electrolyte, providing a visual indicator of activity in attenuating metal deposition, thus reducing metal accumulation on various surfaces in the rechargeable electrochemical storage cell. The natural elastomer obtained from Hevea brasiliensis trees provides superior attenuation of antimony poisoning of the storage cell active surfaces, such as at the negative electrodes, superior attenuation of gassing, water consumption, self discharge and dendritic growth, elevation of top of charge potential as well as superior attenuation of cumulative destructive effects on the structure of the positive electrodes. A suitable quantity of supplement is combined with a suitable quantity of polymeric material to provide a pre-combined material which is conveniently blended with a bulk polymeric material prior to processing into an insulating sheet. This eases handling, permits the use of different types of pre-combined and bulk polymeric materials and minimizes inadvertent loss of supplement during any post processing, such as post-extrusion solvent extraction process. In particular, the supplemented component is a porous insulator typically provided between the positive and negative electrodes of the electrochemical cell. These are structures which are ionically porous but are made of a dielectric material so as to prevent short circuiting between the electrodes.    DETAILED DESCRIPTION - An enhanced-performance rechargeable electrochemical energy storage cell consists of a container, positive electrode(s) with a positive connector (36), and negative electrode(s) with a negative connector (40). The electrodes are arranged in the container, which contains an acidic electrolyte (20). A quantity of an isolated or synthesized performance-enhancing supplement is incorporated with at least one component of the rechargeable electrochemical energy storage cell chosen from container, negative electrode(s), separator(s) arranged between the positive electrode(s) and negative electrode(s), and acidic electrolyte, forming a treated cell. Application of an electric potential across the positive and negative connectors sufficient to cause an electric current to flow in between, effects at least one performance enhancement of the rechargeable electrochemical energy storage cell chosen from reduction of metal transfer within the treated cell, reduction of gas evolution from the treated cell, reduction in water consumption by the treated cell, increase in on-charge potential of the treated cell, reduction in corrosion of the positive electrode of the treated cell, and reduction in self-discharge of the treated cell, when compared to performance of an untreated cell. INDEPENDENT CLAIMS are included for the following:    (1) method for making supplemented rechargeable electrochemical energy storage cell; and    (2) component for use in rechargeable electrochemical energy storage cell.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of two adjacent energy storage cells connected electrically in parallel, in which first cell represents a treated cell and second cell represents a control cell, and a suitable electrical constant current power source.    Enhanced-performance rechargeable electrochemical energy storage cell (10)    Container (16)    Acidic electrolyte (20)    Positive electrode (24)    Negative electrode (28)    Positive connector (36)    Negative connector (40)