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Title: Solid-state sodium batteries using polymer electrolytes and sodium intercalation electrode materials

Solid-state sodium cells using polymer electrolytes (polyethylene oxide mixed with sodium trifluoromethanesulfonate: PEO{sub n}NaCF{sub 3}SO{sub 3}) and sodium cobalt oxide positive electrodes are characterized in terms of discharge and charge characteristics, rate capability, cycle life, and energy and power densities. The P2 phase Na{sub x}CoO{sub 2} can reversibly intercalate sodium in the range of x = 0.3 to 0.9, giving a theoretical specific energy of 440 Wh/kg and energy density of 1,600 Wh/l. Over one hundred cycles to 60% depth of discharge have been obtained at 0.5 mA/cm{sup 2}. Experiments show that the electrolyte/Na interface is stable and is not the limiting factor to cell cycle life. Na{sub 0.7}CoO{sub 2} composite electrodes containing various amounts of carbon black additive are investigated. The transport properties of polymer electrolytes are the critical factors for performance. These properties (the ionic conductivity, salt diffusion coefficient, and ion transference number) are measured for the PEO{sub n}NaCF{sub 3}SO{sub 3} system over a wide range of concentrations at 85 C. All the three transport properties are very salt-concentration dependent. The ionic conductivity exhibits a maximum at about n = 20. The transference number, diffusion coefficient, and thermodynamic factor all vary with salt concentration in a similar fashion,more » decreasing as the concentration increases, except for a local maximum. These results verify that polymer electrolytes cannot be treated as ideal solutions. The measured transport-property values are used to analyze and optimize the electrolytes by computer simulation and also cell testing. Salt precipitation is believed to be the rate limiting process for cells using highly concentrated solutions, as a result of lower values of these properties, while salt depletion is the limiting factor when a dilute solution is used.« less
Authors:
 [1]
  1. Univ. of California, Berkeley, CA (United States). Dept. of Materials Science and Mineral Engineering|[Lawrence Berkeley National Lab., CA (United States). Materials Sciences Div.
Publication Date:
OSTI Identifier:
414308
Report Number(s):
LBNL--39127
ON: DE97001598; TRN: AHC29701%%6
DOE Contract Number:
AC03-76SF00098
Resource Type:
Technical Report
Resource Relation:
Other Information: DN: Thesis submitted to Univ. of California, Berkeley, CA (US); TH: Thesis (Ph.D.); PBD: Aug 1996
Research Org:
Lawrence Berkeley National Lab., CA (United States)
Sponsoring Org:
USDOE Office of Energy Research, Washington, DC (United States)
Country of Publication:
United States
Language:
English
Subject:
25 ENERGY STORAGE; 36 MATERIALS SCIENCE; 40 CHEMISTRY; SOLID ELECTROLYTES; ELECTRICAL PROPERTIES; ELECTROCHEMISTRY; METAL-METAL OXIDE BATTERIES; CATHODES; POLYETHYLENE GLYCOLS; SULFONATES; SODIUM; SODIUM OXIDES; COBALT OXIDES; PERFORMANCE; SODIUM COMPOUNDS; BATTERY CHARGING; EXPERIMENTAL DATA