Mechanistic Insight into the Stability of HfO2-Coated MoS2 Nanosheet Anodes for Sodium Ion Batteries

Bilal Ahmed, Dalaver H. Anjum, Mohamed N. Hedhili, Husam N. Alshareef

Research output: Contribution to journalArticlepeer-review

79 Scopus citations


It is demonstrated for the first time that surface passivation of 2D nanosheets of MoS2 by an ultrathin and uniform layer of HfO2 can significantly improve the cyclic performance of sodium ion batteries. After 50 charge/discharge cycles, bare MoS2 and HfO2 coated MoS2 electrodes deliver the specific capacity of 435 and 636 mAh g-1, respectively, at current density of 100 mA g-1. These results imply that batteries using HfO2 coated MoS2 anodes retain 91% of the initial capacity; in contrast, bare MoS2 anodes retain only 63%. Also, HfO2 coated MoS2 anodes show one of the highest reported capacity values for MoS2. Cyclic voltammetry and X-ray photoelectron spectroscopy results suggest that HfO2 does not take part in electrochemical reaction. The mechanism of capacity retention with HfO2 coating is explained by ex situ transmission electron microscope imaging and electrical impedance spectroscopy. It is illustrated that HfO2 acts as a passivation layer at the anode/electrolyte interface and prevents structural degradation during charge/discharge process. Moreover, the amorphous nature of HfO2 allows facile diffusion of Na ions. These results clearly show the potential of HfO2 coated MoS2 anodes, which performance is significantly higher than previous reports where bulk MoS2 or composites of MoS2 with carbonaceous materials are used. The cyclic stability of MoS2 nanosheet Na-ion battery anodes is improved by depositing a nanoscale HfO2 layer at the electrode/electrolyte interface through atomic layer deposition. The mechanism of capacity retention due to this HfO2 coating is explained by post-electrochemical transmission electron microscopy analysis.

Original languageBritish English
Pages (from-to)4341-4350
Number of pages10
Issue number34
StatePublished - 1 Sep 2015


  • anodes
  • atomic layer deposition
  • MoS
  • nanosheets
  • sodium ion batteries


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