Two-dimensional transition-metal oxide monolayers as cathode materials for Li and Na ion batteries

Abstract

Two-dimensional monolayers are attractive for applications in metal-ion batteries because of their low ion-diffusion barrier and volume expansion. In this work, we carry out a first-principles study on electrochemical and structural properties of two-dimensional (2D) oxide monolayers and investigate their applications in metal-ion batteries. 2D transition-metal oxide monolayers (MO2; M = Mn, Co, and Ni) with various ion-intercalation densities are systematically studied. Our calculations show that Li and Na atoms can easily be transported on the surfaces of the monolayers with low diffusion barriers because of the long binding distance. We find that Li2MO2 and Na2MO2 are stable because of negative intercalation energies and unsaturated specific energies. We show that MnO2 has the lowest diffusion barrier, highest specific capacity, and smallest lattice expansion under Li-intercalation, but lowest cell voltage. We also find that CoO2 shows the largest cell voltages in a wide range of ion-intercalation densities and smallest lattice expansion under Na-intercalation, and NiO2 only gives the highest cell voltage in Li2NiO2 and has the largest volume expansion. We further show that Li and Na atoms in Li2MO2 and Na2MO2 move from stable-adsorption sites to metastable sites on the surfaces of oxide monolayers to reduce lattice expansion, leading to reduced cell voltages. It is expected that metal-ion batteries with particular applications and performances can be achieved in the design of these oxide monolayers.

A First‐Principles Study of Boron‐Doped BC2N Sheet as Potential Anode Material for Li/Na‐Ion Batteries

“…Many 2D materials as anode for LIBs/NIBs have been widely demonstrated in both experiment and theory. For instance, graphene derived from splitting graphite oxide has been widely explored as anode materials . It has been predicted that borophene had a high theoretical capacity (1860 mAh/g), low diffusion barrier and low average open circuit voltage, suggesting its great potential used as anode for LIBs .…”

Intercalation of Layered Materials from Bulk to 2D

“…The favorable ion‐transport properties of 2D metal oxides relative to bulk materials are a driving force behind their exploration . For example, the diffusion barrier for Li in MnO 2 is 0.26 eV in bulk but 0.15 eV in monolayers.…”

Single-layer MnO2 nanosheets for sensitive and selective detection of glutathione by a colorimetric method

“…Owing to its unique physicochemical properties, and environmental and biological compatibility, MnO 2 has attracted wide research interest and found diverse potential applications including cell batteries [23,24], catalyst [25][26][27][28], sensing [29,30], and biological uses in the magnetic resonance imaging and drug delivery [31,32].…”