In situTransmission X-Ray Absorption Fine Structure Analysis of the Charge–Discharge Process in LiMn2O4, a Rechargeable Lithium Battery Material

✍ Scribed by Youhei Shiraishi; Izumi Nakai; Toshio Tsubata; Takuhiro Himeda; Fumishige Nishikawa

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 247 KB
• Volume: 133
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1997.7615

✦ Synopsis

The in situ XAFS technique has been applied for the first time to reveal variations in the local structures of Mn atoms during the charge-discharge process of LiMn 2 O 4 , Li(Mn 1.93 Li 0.07 )O 4 , and Li(Mn 1.85 Li 0.15 )O 4 cathode materials of lithium-ion secondary batteries. It has been demonstrated that the valence state of manganese is in a linear correlation with the peak energy of the Mn K-edge XANES spectrum. EXAFS analysis disclosed the coexistence of Mn 3؉ and Mn 4؉ in LiMn 2 O 4 , with two distinct Mn-O bond distances of 1.98 and 1.88 A s for the Mn 3؉ -O 6 and Mn 4؉ -O 6 octahedra, respectively. Li deintercalation leads to the oxidation of Mn 3؉ to Mn 4؉ and finally to MnO 2 , in which the Mn atom exhibits a uniform octahedral oxygen coordination, with a Mn-O distance of approximately. 1.9 A s The large variation in the local structure around the Mn atom during the charge-discharge process may be responsible for the cyclic instability of the battery material.