Urchin-like Ni2P yolk-shell microspheres with N-doped carbon shells for high-rate and ultralong cycle life K-ion batteries

•Urchin-like Ni2P microspheres are uniformly wrapped into N-doped carbon shells.•The unique urchin-like morphology provides fast charge transfers to active sites.•N-doping carbon can relieve the volume expansions and enhance the conductivity.•The Ni2P@N-C delivers capacity of 172.6 mAh g−1 at 2000 m...

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Bibliographic Details
Published in:Journal of alloys and compounds 2021-09, Vol.875, p.160001, Article 160001
Main Authors: Ye, Jiajia, Xia, Guang, Li, Xuting, Zheng, Zhiqiang, Fu, Zhanghua, Zhang, Qingshuai, Hu, Cheng
Format: Article
Language:English
Subjects:
Anode
Anodes
Carbon
Charge transfer
Ion storage
K ion batteries
Microspheres
Morphology
N-doping carbon
Ni2P@N-C
Nitrogen
Self-assembly
Shells (structural forms)
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Summary:•Urchin-like Ni2P microspheres are uniformly wrapped into N-doped carbon shells.•The unique urchin-like morphology provides fast charge transfers to active sites.•N-doping carbon can relieve the volume expansions and enhance the conductivity.•The Ni2P@N-C delivers capacity of 172.6 mAh g−1 at 2000 mA g−1 after 3000 cycles. [Display omitted] The Ni2P anode own high theoretical capacity but still suffer from big volume expansion thus resulting sluggish electrochemical kinetics in K-ion batteries. Herein, we design and synthesize the urchin-like Ni2P yolk-shell microspheres encapsulated into N-doped carbon shells (Ni2P@N-C) for the first time through one-step hydrothermal followed a phosphidation/carbonization process. The unique urchin-like morphology provides fast charge transfers to the active sites for improved K-ion storage at high current densities. The yolk-shell structure couples with the nitrogen-doping carbon layer to effectively relieve the volume expansions while enhancing the conductivity of the whole anode composite. As a result, Ni2P@N-C electrode delivers an ultrahigh capacity of 172.6 mAh g−1 at 2000 mA g−1 after long time of 3000 cycles and shows outstanding rate performance of 136.6 mAh g−1 at 5000 mA g−1. Lastly, ex situ X-ray diffraction analysis of K+ ion insertion/extraction into/from the Ni2P@N-C electrode shows that potassium ion storage mechanism was to be Ni2P + 3K++3e-↔K3P + 2Ni.
ISSN:0925-8388
1873-4669
DOI:10.1016/j.jallcom.2021.160001