Reversible Lithium Storage with High Mobility at Structural Defects in Amorphous Molybdenum Dioxide Electrode

Abstract

This work demonstrates that structural defects in amorphous metal oxide electrodes can serve as a reversible Li+ storage site for lithium secondary batteries. For instance, molybdenum dioxide electrode in amorphous form (a‐MoO2) exhibits an unexpectedly high Li+ storage capacity (up to four Li per MoO2 unit), which is larger by a factor of four than that for the crystalline counterpart. The conversion‐type lithiation is discarded for this electrode from the absence of Mo metal and lithium oxide (Li2O) in the lithiated a‐MoO2 electrode and the retention of local structural framework. The sloping voltage profile in a wide potential range suggests that Li+ ions are inserted into the structural defects that are electrochemically nonequivalent. This electrode also shows an excellent cycle stability and rate capability. The latter feature is seemingly due to a rather opened Li+ diffusion pathway provided by the structural defects. A high Li+ mobility is confirmed from nuclear magnetic resonance study.

Structure Analyses of Amorphous MoS₃ Active Materials in All-solid-state Lithium Batteries

“…7 A coin-type cell with amorphous MoO 2 electrode showed particularly higher capacity and better rate capability than that of the cell with crystalline MoO 2 . 8 Ku et al reported that the cell performance was improved because the structural defects in amorphous MoO 2 acted as a Li + storage site. Moreover, amorphous phosphorus-carbon composite electrodes in the liquid-type cells using an organic liquid electrolyte showed a high reversible capacity about 1740 mAh g ¹1 for 100 cycles.…”

“…However, reported literature on amorphous electrodes is limited, compared to those of crystalline electrodes. Within that literature amorphous oxide based electrodes, [7][8][9][10][11] amorphous sulfide based electrodes [12][13][14][15][16][17] and amorphous phosphorus based electrodes 18,19 were reported. For example, amorphous V 2 O 5 exhibited better rechargeability than crystalline V 2 O 5 .…”

Li4Ti5O12-rutile TiO2 nanosheet composite as a high performance anode material for lithium-ion battery

“…Surface defect such as surface vacancies or voids is a common phenomenon for nanomaterials. It has been reported that the defects in Li 4 Ti 5 O 12 [44] and amorphous MoO 2 [45] can serve as Li þ storage sites for improved lithium storage capacity and rate performance. Hence, the increased initial capacity of Li 4 Ti 5 O 12 and Li 4 Ti 5 O 12 -rutile TiO 2 nanosheets might also originate from the lattice distortion resulted from the surface vacancies or voids.…”

The beneficial effect of nanocrystalline and amorphous nature on the anode performance of manganese oxide for lithium ion batteries

“…(2) The structural defects in amorphous metal oxide can act as reversible Li + storage sites [46]. (3) The nanometer-level crystal size of metal oxide provides many surface sites for Li + storage due to the expansion of surface area [47].…”