Self-discharge Reactions Research Articles

Novel materials for electrochemical power sources—introduction of PUREBLACK ® Carbons

Graphitization heat treatment of a precursor carbon black was seen to effectively produce a wide variety of forms of partially graphitized nano-sized carbonaceous materials with a set of unique properties, some of which are reported in this paper in comparison with those properties of the precursor carbon material. These novel materials were given the name of PUREBLACK ® Carbons. Among some of the unique properties are: higher conductivity than that of acetylene type carbon blacks due to PUREBLACK ® Carbon's particles having more graphitic structure; very low to zero volatile content (external oxygen, sulfur, etc., groups, which are often believed to be the cause of initiation of self-discharge reactions in batteries); very low equilibrium moisture pickup (20 ppm level), which makes it particularly attractive in lithium metal or lithium-ion based electrochemical systems; high purity. Electrochemical testing of the newly proposed PUREBLACK ® Carbons in several battery systems offers significant promise that it presents a viable solution to the needs of industry.

Electrochemical Activity of Hydrothermally Synthesized Li-Ti-O Cubic Oxides toward Li Insertion

Li-Ti-O oxides prepared by hydrothermal synthesis are active hosts for lithium insertion. Annealing of synthesized samples at temperatures above 250°C leads to structural water removal, which causes narrowing of voltammetric peaks and, subsequently, shift of the insertion potential toward more negative potentials. An increase of annealing temperature also improves coulombic efficiency and stability against self-discharge reactions. On the other hand, the lithium insertion/extraction kinetics slows down with increasing annealing temperature. Hydrothermally synthesized Li-Ti-O spinels show more favorable charge transfer kinetics as well as lithium transport comparing with spinels prepared at 800°C. Thermodynamics of Li insertion into hydrothermally prepared phases can be described by the Frumkin insertion isotherm. The low temperature prepared spinels seem to be less susceptible to a lithium-insertion triggered phase transition than the high temperature synthesized materials. © 2002 The Electrochemical Society. All rights reserved.

ChemInform Abstract: SELF‐DISCHARGE IN ACID‐STARVED LEAD‐ACID BATTERIES

AbstractKurven der Batteriespannung als Funktion der Zeit werden zur Untersuchung der Selbstentladungsreaktionen in Pb‐H, SO4‐KFZ‐Batterien benutzt.

ChemInform Abstract: SELF‐DISCHARGE AND PASSIVATION PHENOMENA IN LEAD‐ACID BATTERIES DURING STORAGE

During storage of partially wet-charged and dry-charged lead-acid batteries, processes take place which lead to self-discharge and passivation of the plates. In the case of partially wet-charged batteries, PbSO/sub 4/ crystals form in the separators during storage. When the battery is subjected to charge and overcharge they transform into Pb and PbO/sub 2/ and cause short circuits between the plates and the failure of the battery. Self-discharge reactions are presented for the two kinds of plates. The capacity loss during storage is reversed upon charge of the battery. The passivation phenomena are determined by the structure of the two kinds of plates. The passivation of the positive plate manifests itself by an abrupt fall of its discharge potential. It is assumed that this is due to the formation of a nonstoichiometric oxide following a reaction between the grid and PbO/sub 2/ of the corrosion layer. 13 refs.