Li3VO4: A Promising Insertion Anode Material for Lithium-Ion Batteries
Li3VO4: A Promising Insertion Anode Material for Lithium-Ion Batteries
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DOI：
10.1002/aenm.201200833
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发表时间：
2013-04-01
影响因子：
27.8
通讯作者：
Zhou, Haoshen
中科院分区：
文献类型：
--
作者：
Li, Huiqiao;Liu, Xizheng;Zhou, Haoshen
石墨被用作商用锂电池的主要阳极，但其比容量限制为每c6 1 Li+（理论上对应于372 mAh g−1）。此外，石墨以接近镀锂的低电位插入锂，由于表面镀锂高（锂枝晶，可能导致短路），存在安全风险。人们已经做了很多努力来寻找石墨的替代品，希望找到比Li/Li+具有更大容量和更高正插层电压的材料。[1,2]所提出的阳极材料根据其反应机理可分为三大类：(1)插层/脱插反应，典型为ti基氧化物；(2)合金/脱合金工艺，主要指硅、锡基合金及复合材料；(3)转换反应，涉及大多数过渡金属氧化物，金属硫化物等。合金型阳极每Si或Sn能够承载4.4 mol Li，因此可以提供超高容量。不幸的是，如此多的锂的容纳伴随着宿主金属的巨大体积变化（> 300%）。在循环过程中，巨大的体积变化导致晶格应力和相应的合金颗粒开裂和破碎，导致在几个充放电循环中容量突然损失转换型材料可以提供2 ~ 3倍于石墨的容量，但它们的第一次放电过程导致其主体结构的非晶化，并且与能量势垒和触发MO键断裂相关的不良动力学导致了大的电极极化由此产生的低能量效率和高反应电压使得在高能电池系统中使用转换型材料不切实际。嵌入反应是指可移动的客体物质（这里是Li+）可逆地插入到含有相互连接的空晶格位点（活性位点）框架的晶体宿主（电极化合物）中，而宿主晶格的结构完整性在形式上是守恒的。由于其高可逆性和高能效，已被证明是lib历史上最成功的机制。然而，迄今为止，除了钛基氧化物和碳质材料外，还发现了少数几种具有良好阳极性能的化合物。除石墨外，尖晶石Li 4Ti 50o12是另一种公认的插入型阳极，以其最小的结构变化和Li插入/提取时的高可逆性而闻名与零应变下的Li/Li+相比，锂离子插入Li 4Ti 50o12的电压约为1.5 V，因此具有显著提高的安全性能和良好的循环稳定性。然而，其有限的容量（~ 150mah g−1）以及如此高的工作电压严重牺牲了电池电压和电池能量。如图1所示，如果两者与典型的4v阴极耦合，则Li 4Ti 50o 12的估计能量密度（关于电位和容量）不超过石墨的三分之一。因此，寻找一种容量大、插入电位合适的新型插入阳极具有重要的意义。层状钒氧化物，如V2o - 5， v6013, LiV - 308，作为Li+插层的有效宿主材料已被广泛探索。[6-8] Li+的插入通常发生在高于2.5 V vs. Li/Li+的电位下，因此它们被视为阴极材料。在这里，我们首次关注了另一种钒氧化物Li 3VO 4，并发现它在0.5 ~ 1.0 V vs. Li/Li+电压下插入Li离子，低于Li 4Ti 50o12的电压。此外，它表现出与……相当的能力。
Graphite is used as the dominant anode in commercial LIBs, but its specific capacity is limited to 1 Li+ per C 6 (corresponding to 372 mAh g− 1 theoretically). Besides, graphite intercalates Li at a low potential close to that of the Li-plating, which results in a safety risk due to high surface Li-plating (Li dendrite, a potential cause of short circuits). Many efforts have been made to search for graphite alternatives in the hope of finding materials with both large capacities and slightly more positive intercalation voltages compared to Li/Li+.[1, 2] The proposed anode materials can be divided into three main categories according to their reaction mechanisms:(1) the intercalation/de-intercalation reaction, typically as Ti-based oxides;(2) the alloy/de-alloy process, mainly referring to Si-and Sn-based alloys and composites;(3) the conversion reactions, referring to most transition metal oxide, metal sulfides etc.[3] The alloy type anodes are capable to host 4.4 mol Li per Si or Sn, thus can deliver ultrahigh capacities. Unfortunately, the accommodation of so much lithium is accompanied by enormous volume changes (> 300%) in the host metal. The huge volume change leads to lattice stress and consequential cracking and crumbling of the alloy particles during cycling, resulting in abrupt loss in capacity within a few charge/discharge cycles.[1] The conversion type materials can deliver a capacity 2∼ 3 times of that for graphite, but their first discharge process leads to the amorphization of their host structures, and the poor kinetics associated with the energy barrier and trigger breakage of the MO bonds causes a large electrode polarization.[4] The resulting poor energy efficiency together with a high reaction voltage makes the use of conversion type material impractical in a high energy battery system. The intercalation reaction refers to the reversible insertion of mobile guest species (here Li+) into a crystalline host (electrode compound) that contains an interconnected framework of empty lattice sites (active sites), while the structural integrity of the host lattice is formally conserved. It has been proved to be the most successful mechanism in the history ofLIB due to the high reversibility and high energy efficiency. However, a limited number of compounds, apart from Ti-based oxides and carbonaceous material, have been found to show promising anode performances up to now. Apart from graphite, spinel Li 4Ti 5O 12 is another well recognized insertion type anode known for its minimal structure change and high reversibility upon Li insertion/extraction.[5] The insertion of lithium ions into Li 4Ti 5O 12 occurs at about 1.5 V vs. Li/Li+ with zero strain, thus it exhibits significantly improved safety performance and excellent cycling stability. However, its limited capacity (∼ 150 mAh g− 1) along with such a high operation voltage sacrifices the cell voltage and cell energy seriously. As shown in Figure 1, the estimated energy density of Li 4Ti 5O 12 (regarding both potential and capacity) does not exceed one third of that for graphite if the two are coupled with a typical 4 V cathode. So, it would be of great interest to find a new insertion anode with large capacity and appropriate insertion potential. Layered vanadium oxides, eg V2o 5, V6o 13, LiV 3O 8, have been extensively explored as effective host materials for Li+ intercalation.[6–8] The insertion of Li+ usually takes place at a potential higher than 2.5 V vs. Li/Li+, thus they are seen as cathode materials. Here, we, for the first time, focused on another vanadium oxide, Li 3VO 4, and found that it intercalates Li ions at a voltage mainly between 0.5∼ 1.0 V vs. Li/Li+, lower than that of Li 4Ti 5O 12. Besides, it exhibited a capacity comparable to …