Charge Compensation Mechanism during Cycles in Fe-Containing Li₂MnO₃ Cathode for High Energy Density and Low-Cost Lithium-Ion Batteries

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• 作者：Ryota Yuge^a ; ^{r-yuge@bk.jp.nec.com" class="auth_mail" title="E-mail the corresponding author} ; Akio Toda^a ; Sadanori Kuroshima^a ; Hideyuki Sato^a ; Takashi Miyazaki^a ; Noriyuki Tamura^a ; Mitsuharu Tabuchi^b ; Kentaro Nakahara^a
• 关键词：Lithium ion battery ; Fe-containing lithium-rich layered manganese oxides ; X-ray absorption spectroscopy ; Soft-X-ray absorption spectroscopy
• 刊名：Electrochimica Acta
• 出版年：2016
• 出版时间：20 January 2016
• 年：2016
• 卷：189
• 期：Complete
• 页码：166-174
• 全文大小：2225 K

文摘

The charge compensation mechanism during cycles was investigated in Fe-containing lithium-rich layered manganese oxides (Li_1.26Mn_0.52Fe_0.22O₂), which has a potential to be used as cathode materials for high energy density and low-cost lithium-ion batteries. The capacity of cells with Li_1.26Mn_0.52Fe_0.22O₂ cathode in the discharged state was 234 mAhg⁻¹ and the capacity retention was 46% at 30 cycles for the limit voltage from 2.0 to 4.8 V. X-ray diffraction measurements and the X-ray Rietveld analysis indicated that a layered rock-salt structure for the discharge states was transformed into a mixture of the layered rock-salt and spinel structure during cycles and that the ratio of the spinel phase became 32% by weight at 30 cycles. The X-ray absorption spectroscopy (XAS) and soft-XAS measurements revealed that the valence modification from Mn⁴⁺ to Mn^2+/3+, Fe⁴⁺ to Fe³⁺, and O₂²⁻ to O²⁻ for the charge-discharge occurred together during cycles. During 30 cycles, the redox reactions of Fe, Mn, and oxide ions gradually became irreversible. Primary cause of above phenomena was that Fe and Mn ions stabilized at Fe³⁺ and Mn²⁺ from the surface of the electrode with the structural transformation from the layered rock-salt phase to the spinel phase.