L.A. Montoro

Gelatin/DMSO: a new approach to enhancing the performance of a pyrite electrode in a lithium battery

Abstract We have studied the electrochemical behavior of natural pyrite (FeS 1.9 , n-type semiconductor) treated nonaqueously with dimethylsulfoxide (DMSO) solvent and also with a gelatin/DMSO solution. Composite electrodes (comprised of pyrite, polyvinilidene fluoride, polyethylene oxide and carbon) were characterized in a lithium cell at room temperature by cyclic voltammetry and galvanostatic measurements; the electrolyte used was LiPF 6 in a solution of ethylene carbonate and dimethyl carbonate (1 mol l −1 ). The gelatin/DMSO treatment greatly improved the reversible specific capacity of a pyrite electrode. For galvanostatic discharge/charge at a current density of 0.4 mA cm −2 and between voltage limits of 3.2 and 1.1 V, its reversible specific capacity at the 15th cycle equaled 275 mA h g −1 , an impressive value compared to less than 25 mA h g −1 for a pristine pyrite electrode.

Changes in the Electronic Structure of Chemically Deintercalated LiCoO2

We studied the changes in the electronic structure of induced by deintercalation using and X‐ray absorption spectroscopy. The mean probing depth of this technique is . The results were analyzed using atomic multiplet and band structure calculations. The spectrum shows that the ions in are in a trivalent low‐spin state. The spectra of deintercalated show only minor changes as a function of concentration. The absence of changes indicates that the ions remain mostly unaffected by deintercalation. In particular, the ions in deintercalated are not oxidized to a tetravalent state as normally assumed. The spectra of deintercalated show an increase in the absorption intensity below threshold; this absorption increase indicates that the ions in are reduced upon deintercalation. ©2000 The Electrochemical Society