High-Voltage LiNi1/2Mn3/2O4 Spinel: Cationic Order and Particle Size Distribution

详细信息    查看全文

• 作者：Svetlana Ivanova ; Ekaterina Zhecheva ; Radostina Stoyanova ; Diana Nihtianova ; Sebastian Wegner ; Pavleta Tzvetkova ; Svetlana Simova
• 刊名：Journal of Physical Chemistry C
• 出版年：2011
• 出版时间：December 22, 2011
• 年：2011
• 卷：115
• 期：50
• 页码：25170-25182
• 全文大小：1339K
• 年卷期：v.115,no.50(December 22, 2011)
• ISSN：1932-7455

文摘

Lithium鈥搉ickel manganese spinel, LiNi_1/2Mn_3/2O₄, is capable to intercalate lithium reversible at a high voltage delivering a high specific energy when used as cathode material for lithium ion batteries. In this study, the effects of cationic order and particle size distribution on the lithium intercalation in high-voltage LiNi_1/2Mn_3/2O₄ spinel are examined by the application of diffraction and spectroscopic techniques. At 400 掳C, nonstoichiometric LiNi_1/2Mn_3/2O_4-未 with a disordered spinel structure and particle size distribution between between 10 and 20 nm is obtained. ⁷Li NMR with ultrafast spinning rates and electron paramagnetic resonance spectroscopy show that Ni²⁺, Mn³⁺, and Mn⁴⁺ ions are nonuniformly distributed forming nanoscale domains with (Ni²⁺,Mn⁴⁺)-, (Ni²⁺,Mn⁴⁺,Mn³⁺)-, and (Mn³⁺,Mn⁴⁺) compositions, respectively, the entirely cubic spinel structure being preserved. By increasing the annealing temperature, the amount of Mn³⁺ decreases, and Ni²⁺ and Mn⁴⁺ tend to set up a long-range order. The particles start to grow above 600 掳C, reaching submicrometer dimensions at 800 掳C. Acid treatment of ordered submicrometer LiNi_1/2Mn_3/2O₄ modifies the particle size distribution without change of the cationic distribution. Cationic Ni,Mn distribution affects the Li⁺ extraction/insertion from/into LiNi_1/2Mn_3/2O₄, while the particle size distribution has an impact on the rate capability and on the interaction with the electrolyte. After storing of the spinels in electrolyte solutions, the nanosized particles are covered with LiF/Li_xPF_yO_z/P₂O₅, while Ni,MnF₂/Li_xPF_y compounds are deposited on the surface of the submicrometer particles. Ordered LiNi_1/2Mn_3/2O₄ with a three-modal particle size distribution displays the best rate capability.