Electrochemical and spectroscopic measurements were used to characterize the electrochromic behavior of sputtered V 20 5 films. In response to lithium intercalation, the fundamental optical absorption edge of V 20 5 shifts to high energies by 0.20-0.31 eV as the lithium concentration increases from Li o . o V 20 5 to Lio.86 V 20S' There is a corresponding increase in the near-infrared absorption that exhibits Beer's law behavior at low lithium concentrations. The shift in absorption edge results in a large decrease in absorbance in the 350-4:50 nm wavelength range. This effect is most prevalent in thin films which exhibit a yel10w to colorless optical modulation on lithium intercalation. The cathodic coloration in the near infrared is relatively weak with a maximum coloration efficiency of 35 cm 2 /C [This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP: 137.

The chemistry of normalLi/SOCl2 cells containing normalBrCl , popularly known as BCX cells, has been investigated. normalBrCl significantly modifies the chemistry of the normalLi/SOCl2 cell. The discharge of the normalBrCl in the cell proceeds through the reductions of Cl2 , Br2 , and normalBrCl . The normalLiBr formed appears to react with SOCl2 to generate sulfur bromides, SO2Br2 , Br2 , and normalLiCl . Sulfur halides are also formed in the cell by the reaction of Cl2 , normalBrCl , or Br2 with S produced by the reduction of SOCl2 . Addition of normalBrCl appears to have an adverse effect on the storability of the normalLi/SOCl2 cell after partial discharge.

Rechargeable, solid-state Li batteries employing polymer electrolytes are being actively pursued as possible power sources for a variety of applications (1-3). Complexes of Li salts such as LiCF~SO3, LiCI04 or LiBF 4 with poly-(ethylene oxi~e)-(PEO) have been the most widely studied polymer electrolytes in cells utilizing Li anodeand a rechargeable cathode such as TiS~ (I) or V6013 (3).Because of their low Li conductivity, cells employing PEO electrolytes exhibit reasonable rate capabilities only at around lO0~The discovery (4) that the Li + salt complexes of poly[bis(methoxyethoxyethoxide)phosphazene], or MEEP, have significantly higher ambient temperature Li + conductivities than the PEO-based electrolytes offered potential opportunites for the fabrication of polymer electrolyte Li batteries for operation at or near room temperature.However, the liquidlike properties of the MEEP electrolyte, i.e., its tendency to flow, although desirable from conductivity point of view, prevented the preparation of dimensionally stable, thinfilm electrolytes, necessary for the construction of practical solid-state batteries.We report here on a novel approach to utilize the excellent conducting properties of the MEEP-based electrolytes in solid-state Li batteries.We have blended PEO with MEEP to enhance the latter's dimensional stability, enabling the fabrication of thin-film electrolytes with significantly higher conductivity than pure PEO electrolytes.Initial results suggest that this approach can lead to solidstate Li cells with significantly improved discharge rate and cycling capabilities than those possible by the use of presently available polymer electrolytes.MEEP, doped with LiCF3SO 3 or LiClO 4 in a 4:1 mole ratio for the monomer repeat unit to Li +, was prepared according to_published procedures (4,5). PEO (MW = 5 x i0 b) was obtained from Polyscience, Inc. The MEEP and PEO were mixed in 50:50 and 80:20 weight ratios in *Electrochemical Society Active Member. Key Words: Solid-state lithium batteries. 535 acetonitrile. Li salts were added so that the O/Li + ratio in the above mixtures was 8 for the amount of PEO present.Films were cast by pouring the acetonitrile solutions of the above mixtures onto Teflon dishes and slowly evaporating the solutions at room temperature inside an Ar-filled glove box. The resulting films, having a thickness of-4 mil, were dried under vacuum at 100oc for 3 to 4 hours. Conductivity measurements at selected temperatures were carried out using the ac impedance technique with stainless steel ionblocking electrodes between 5 Hz and 200 kHz. ExperimentalLi/TiS 2 cells were constructed with the polymer electrolyte sandwiched between a Li foil anode pressed onto Ni screen and a TiS~ composite cathode. These cathodes of 2 miJ thickness and ~1.5 mAh/cm 2 theoretical capacity were prepared by spreading a mixture of 80 w/o TiS 2, prepared inhouse, and 20 w/o PEO/LiCIO 4 onto one side of a Ni foil. All the cells were constructed cathode-limited. The electrode package was secured between stainless stee...

No abstract

Abstract(BCX cell).