Metal-Organic Framework-Derived Nanoconfinements of CoF2 and Mixed-Conducting Wiring for High-Performance Metal Fluoride-Lithium Battery
Metal-Organic Framework-Derived Nanoconfinements of CoF2 and Mixed-Conducting Wiring for High-Performance Metal Fluoride-Lithium Battery
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金属有机框架衍生的 CoF2 纳米限制和高性能金属氟化物锂电池的混合导电布线
DOI：
10.1021/acsnano.0c08918
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发表时间：
2021
期刊：
影响因子：
17.1
通讯作者：
Yu Yan
中科院分区：
文献类型：
--
作者：
Wu Feixiang;Srot Vesna;Chen Shuangqiang;Zhang Mingyu;van Aken Peter A.;Wang Yong;Maier Joachim;Yu Yan
金属氟化物（MF）转换阴极理论上比镍基或钴基插入氧化物阴极具有更高的重量和体积容量，这使得金属氟化物锂电池成为下一代高能量密度电池的有希望的候选者。然而，它们的高能量特性受到低容量利用率、大电压迟滞和差循环稳定性的影响。造成这种情况的原因有很多：反应动力学差、电导率低、MF/电解质界面不稳定以及循环时活性物质的溶解。本文中，我们将金属有机骨架（MOF）的合成与低温氟化相结合，制备了MOF形状的CoF2@C纳米复合材料，该复合材料在生产的结构中表现出对cof2纳米粒子的限制和高效的混合导电布线。超小的cof2纳米颗粒（平均5-20 nm）被石墨碳壁均匀覆盖并嵌入多孔碳框架中。在CoF2@C纳米复合材料中，交联的碳壁和相互连接的纳米孔分别作为电子和离子传导途径，实现了CoF2的高度可逆转化反应。因此，生产的CoF2@C复合阴极成功地抑制了上述挑战，并表现出0.2C时~ 500 mAh g- 1的高容量利用率，良好的倍率能力（高达2C），以及超过400次循环的长期循环稳定性。总的来说，本研究不仅报告了一种简单的复合设计，以实现CoF2-Li电池的高能量特性，而且可能为许多其他金属氟化锂电池提供通用解决方案。
Metal fluoride (MF) conversion cathodes theoretically show higher gravimetric and volumetric capacities than Ni- or Co-based intercalation oxide cathodes, which makes metal fluoride–lithium batteries promising candidates for next-generation high-energy-density batteries. However, their high-energy characteristics are clouded by low-capacity utilization, large voltage hysteresis, and poor cycling stability of transition MF cathodes. A variety of reasons is responsible for this: poor reaction kinetics, low conductivities, unstable MF/electrolyte interfaces and dissolution of active species upon cycling. Herein, we combine the synthesis of the metal–organic-framework (MOF) with the low-temperature fluorination to prepare MOF-shaped CoF2@C nanocomposites that exhibit confinement of the CoF2nanoparticles and efficient mixed-conducting wiring in the produced architecture. The ultrasmall CoF2nanoparticles (5–20 nm on average) are uniformly covered by graphitic carbon walls and embedded in the porous carbon framework. Within the CoF2@C nanocomposite, the cross-linked carbon wall and interconnected nanopores serve as electron- and ion-conducting pathways, respectively, enabling a highly reversible conversion reaction of CoF2. As a result, the produced CoF2@C composite cathodes successfully restrain the above-mentioned challenges and demonstrate high-capacity utilization of ∼500 mAh g–1at 0.2C, good rate capability (up to 2C), and long-term cycle stability over 400 cycles. Overall, the presented study not only reports on a simple composite design to achieve high-energy characteristics in CoF2–Li batteries but also may provide a general solution for many other metal fluoride–lithium batteries.