Synthesis, characterization, and electrochemical properties of amorphous CrO{sub 2{minus}{delta}} (0 {le} {delta} {le} 0.5) cathodes
- Univ. of Texas, Austin, TX (United States). Center for Materials Science and Engineering
Amorphous chromium oxides CrO{sub 2{minus}{delta}} (0 {le} {delta} {le} 0.5) have been synthesized by a reduction of K{sub 2}CrO{sub 4} with KBH{sub 4} in aqueous solutions. The samples have been characterized by x-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, transmission electron microscopy, and iodometric titration. The oxidation state of Cr and the total oxygen content (2 {minus} {delta}) generally decrease with increasing volume of KBH{sub 4} at a given pH or with increasing pH at a given volume of KBH{sub 4}. The amorphous CrO{sub 2{minus}{delta}} samples lose oxygen sharply at 400 < T < 600 C to give crystalline Cr{sub 2}O{sub 3}; the temperature at which oxygen loss occurs increases from about 400 C for {delta} {approx} 0 to about 600 C for {delta} {approx} 0.5. The capacity of the amorphous CrO{sub 2{minus}{delta}} cathodes decreases with increasing {delta} due to a decreasing oxidation state of Cr. Amorphous CrO{sub 2} shows a maximum initial capacity of 180 mAh/g in the range 3.3 to 2.3 V for a current density of 0.1 mA/cm{sup 2}. Although the capacity declines during the initial cycles, it becomes stable after about 20 cycles, for example, at about 90 mAh/g for 0.5 mA/cm{sup 2}.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 556829
- Journal Information:
- Journal of the Electrochemical Society, Vol. 144, Issue 9; Other Information: PBD: Sep 1997
- Country of Publication:
- United States
- Language:
- English
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