Full picture discovery for mixed-fluorine anion effects on high-voltage spinel lithium nickel manganese oxide cathodes
Full picture discovery for mixed-fluorine anion effects on high-voltage spinel lithium nickel manganese oxide cathodes
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DOI：
10.1038/am.2017.90
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发表时间：
2017-07-07
影响因子：
9.7
通讯作者：
Teshima, Katsuya
中科院分区：
文献类型：
--
作者：
Kim, Dae-wook;Shiiba, Hiromasa;Teshima, Katsuya
少量的氟取代氧的不足可以减少Mn的溶解，提高尖晶石型锂镍锰氧化物（LiNi0.5Mn1.5O4）的循环性能。氟阴离子的掺入同时增强了C-速率能力和比容量衰减。我们使用实验和理论方法来全面了解LiNi0.5Mn1.5O4-xFx阴极材料的混合阴离子效应。氟阴离子降低了锂离子沿沿着能量上最优选的8a-16 c-8a路线跳跃的活化势垒，增强了C速率能力。同时，线性F-Mn 3 +-F-（Mn@2F对角线）排列的配位键将氧化电位提高到5.1V（相对于Li+/Li）。这阻碍了Li+从尖晶石晶格中的完全提取，这是由低于截止电压（3.5- 4.8V（相对于Li+/Li））的Mn 3+的氧化触发的，导致容量损失。
Small amounts of fluorine substituting for oxygen deficiencies could reduce Mn dissolution, enhancing the cyclability in spinel-type lithium nickel manganese oxides (LiNi0.5Mn1.5O4). Fluorine anion incorporation simultaneously enhances the C-rate capability and specific capacity fading. We used experimental and theoretical approaches to obtain a full picture of the mixed-anion effects for LiNi0.5Mn1.5O4-xFx cathode materials. The fluorine anion reduced the activation barrier for lithium-ion hopping along the most energetically preferable 8a-16c-8a route, enhancing the C-rate capability. Simultaneously, the coordination bond of the linear F--Mn3+-F- (Mn@2F diagonal) arrangement increased the oxidation potential to 5.1 V (vs Li+/Li). This hampered full extraction of Li+ from the spinel lattice, which was triggered by the oxidation of Mn3+ below the cutoff voltage (3.5-4.8 V (vs Li+/Li)), leading to a capacity loss.