Structure Investigation and Electrochemical Behavior of γ-MnO2 Synthesized from Three-Dimensional Framework and Layered Structures

✍ Scribed by Kh.S. Abou-El-Sherbini

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 205 KB
• Volume: 166
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2002.9608

✦ Synopsis

MnO 2 was chemically prepared from birnessite (CMD 2D ) and from spinel-like LiMn 2 O 4 (CMD 3D ) by acid leaching. X-ray diffractometry, FTIR spectrometry, chemical and thermal analyses were used to determine the structure and chemical disorder. On the basis of cation vacancy model, the structural water was found to be mainly due to Coleman protons in both samples. Both samples were found to be of very close structure belonging to c-MnO 2 type I according to Chabre and Pannetier classification with de Wolff disorder (P r ) of 0.19 and 0.30 and microtwinning (Tw) of 9.9 and 17%, respectively. The activation energy of structural water release calculated from thermal analysis was apparently higher than that of other c-MnO 2 types (150 and 156.6 kJ/mol, respectively).

A high reduction capacity in aqueous and non-aqueous batteries was delivered for both samples except for the electrochemical lithium insertion of CMD 2D , which was attributed to the different oxygen packing.