| Autor: |
Zhao Z, Tian G, Sarapulova A, Melinte G, Gómez-Urbano JL; CIC energiGUNE , Parque Tecnológico C/Albert Einstein 48 , 01510 Miñano , Alava , Spain., Li C, Liu S; International Center for New-Structured Materials (ICNSM) , Zhejiang University (ZJU) , Zheda Road 38 , 310027 Hangzhou , P. R. China., Welter E; Deutsches Elektronen-Synchrotron DESY , Notkestrasse 85 , D-22607 Hamburg , Germany., Etter M; Deutsches Elektronen-Synchrotron DESY , Notkestrasse 85 , D-22607 Hamburg , Germany., Dsoke S; Helmholtz-Institute Ulm for Electrochemical Energy Storage (HIU) , Helmholtzstrasse 11 , 89081 Ulm , Germany. |
| Abstrakt: |
The carbon coating strategy is intensively used in the modification of conversion-type anode materials to improve their cycling stability and rate capability. Thus, it is necessary to elucidate the modification mechanism induced by carbon coating. For this purpose, bare ZnMn 2 O 4 , carbon-derivative-coated ZnMn 2 O 4 , and carbon-coated ZnO-MnO composite materials have been synthesized and investigated in-depth. Herein, high-temperature synchrotron radiation diffraction is used to monitor the phase transition from ZnMn 2 O 4 to ZnO-MnO composite during the carbonization process. The electrochemical performance has been evaluated by cyclic voltammetry, galvanostatic cycling, and electrochemical impedance spectroscopy. The carbon- and carbon-derivative-coated samples display well-improved cycling stability in terms of suppressed electrode polarization, a moderate increase in resistance, and slight capacity variation. The influence of carbon coating on the intrinsic conversion process is investigated by ex situ X-ray absorption spectroscopy, which reveals the evolution of Zn and Mn oxidation states. This result confirms that the strong capacity variation of the bare ZnMn 2 O 4 is induced not only by the reversible charge storage in the solid electrolyte interphase but also by the phase evolution of active materials. Carbon coating is an effective method to prevent the additional oxidation of MnO to Mn 3 O 4 , which leads to a stabilization of the main conversion reaction. |
