Azo Compounds Derived from Electrochemical Reduction of Nitro Compounds for High Performance Li-Ion Batteries
Azo Compounds Derived from Electrochemical Reduction of Nitro Compounds for High Performance Li-Ion Batteries
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DOI：
10.1002/adma.201706498
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发表时间：
2018-06-06
影响因子：
29.4
通讯作者：
Wang, Chunsheng
中科院分区：
文献类型：
--
作者：
Luo, Chao;Ji, Xiao;Wang, Chunsheng
有机化合物是可持续锂离子电池电极的理想替代品。然而，目前最先进的有机电极的电化学性能仍然不如商用无机电极。本文报道了一种用于高性能锂离子电池的新化学方法，即将硝基化合物电化学转化为偶氮化合物。以4-硝基苯甲酸锂盐(NBALS)为模型硝基化合物，系统研究了硝基化合物的结构、锂/脱硫化机理及电化学性能。NBALS在0.5C时的初始容量为153mAhg(-1)，100次循环后的容量为131mAhg(-1)。详细的表征表明，在初始的电化学锂化过程中，晶态NBALS中的硝基被不可逆地还原为无定形的偶氮化合物。随后，偶氮化合物在接下来的充放电循环中被可逆地锂化/脱硫化，具有高的电化学性能。通过直接使用偶氮化合物作为电极材料验证了偶氮化合物的锂/脱硫化机理，这些化合物表现出与硝基化合物相似的电化学性能，而具有更高的初始库仑效率。因此，这项工作证明了硝基化合物可以电化学转化为偶氮化合物，用于高性能锂离子电池。
Organic compounds are desirable alternatives for sustainable lithium-ion battery electrodes. However, the electrochemical properties of state-of-the-art organic electrodes are still worse than commercial inorganic counterparts. Here, a new chemistry is reported based on the electrochemical conversion of nitro compounds to azo compounds for high performance lithium-ion batteries. 4-Nitrobenzoic acid lithium salt (NBALS) is selected as a model nitro compound to systemically investigate the structure, lithiation/delithiation mechanism, and electrochemical performance of nitro compounds. NBALS delivers an initial capacity of 153 mAh g(-1) at 0.5 C and retains a capacity of 131 mAh g(-1) after 100 cycles. Detailed characterizations demonstrate that during initial electrochemical lithiation, the nitro group in crystalline NBALS is irreversibly reduced into an amorphous azo compound. Subsequently, the azo compound is reversibly lithiated/delithiated in the following charge/discharge cycles with high electrochemical performance. The lithiation/delithiation mechanism of azo compounds is also validated by directly using azo compounds as electrode materials, which exhibit similar electrochemical performance to nitro compounds, while having a much higher initial Coulombic efficiency. Therefore, this work proves that nitro compounds can be electrochemically converted to azo compounds for high performance lithium-ion batteries.