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Morphology Processing by Encapsulating GeP5 Nanoparticles into Nanofibers toward Enhanced Thermo/Electrochemical Stability

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posted on 2018-09-04, 00:00 authored by Yaqing Wei, Jiajun Chen, Jun He, Ruihuan Qin, Zhi Zheng, Tianyou Zhai, Huiqiao Li
Compared with elemental phosphorus, GeP5, with much better thermostability and super higher conductivity, can exhibit a comparable capacity (>2000 mA h g–1) with a much higher first Coulombic efficiency (95%) for lithium-ion batteries. However, such high capacity is accompanied by large volume expansions, leading to fast capacity fading. To improve the cycle stability, fabricating a special nanostructure to reduce the volume stress and compositing with a carbon matrix to buffer the volume change are highly required. However, nanostructured metal phosphides were rarely reported up to now because they are difficult to be synthesized via a normal wet chemistry method or gas phosphorization because of lack of proper reactants and poor thermostability of phosphides. Herein, we successfully achieve uniform carbon-encapsulated GeP5 nanofibers (GeP5@C-NF) by processing GeP5 nanoparticles into carbon nanofibers via electrospinning. After carbon encapsulation, the thermostability of GeP5 can be greatly improved to over 600 °C for higher battery safety. Such a nanofiber structure in which nanosized GeP5 is embedded in a carbon matrix can greatly accommodate the large volume changes during lithiation and provide fast electron transportation, thus contributing to a long cycle life (>1000 mA h g–1 after 200 cycles) and high rate performance (803 mA h g–1 at 2000 mA g–1). This morphology processing technique can be easily extended to other metal phosphide anodes which are limited by a lack of appropriate synthesis methods and poor thermostability.

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