In Situ XAFS Analysis of Li(Mn, M)2O4 (M=Cr, Co, Ni) 5V Cathode Materials for Lithium-Ion Secondary Batteries
✍ Scribed by Yasuko Terada; Kenji Yasaka; Fumishige Nishikawa; Tokuzo Konishi; Masaki Yoshio; Izumi Nakai
- Publisher
- Elsevier Science
- Year
- 2001
- Tongue
- English
- Weight
- 169 KB
- Volume
- 156
- Category
- Article
- ISSN
- 0022-4596
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✦ Synopsis
Chemical states and structural changes accompanying the electrochemical Li deintercalation of Li 1؊x (Mn, M) 2 O 4 (M ؍ Cr, Co, Ni) were studied by the in situ X-ray absorption 5ne structure (XAFS) technique. The X-ray absorption near-edge structures (XANES) of Mn and M as a function of x showed that the high voltage ( &5 V) in the cathode materials of an Li secondary battery is due to the oxidation of M 3؉ to M 4؉ (M ؍ Cr, Co) and M 2؉ to M 4؉ (in the case of M ؍ Ni), while the origin of the low voltage (3.9+4.3 V) can be ascribed to the oxidation of Mn 3؉ to Mn 4؉ . The extended X-ray absorption 5ne structure (EXAFS) analysis of Li 1؊x (Mn, Ni) 2 O 4 revealed that Ni 2؉ is oxidized to Ni 4؉ via the Ni 3؉ state with a Jahn+Teller distorted Ni 3؉ +O octahedron.