Defect, Diffusion and Dopant Properties of NaNiO2: Atomistic Simulation Study

Ruwani Kaushalya,Poobalasuntharam Iyngaran,Navaratnarajah Kuganathan,Alexander Chroneos

doi:10.3390/en12163094

Ruwani Kaushalya, Poobalasuntharam Iyngaran + Show 2 more

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https://doi.org/10.3390/en12163094

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Abstract

Sodium nickelate, NaNiO2, is a candidate cathode material for sodium ion batteries due to its high volumetric and gravimetric energy density. The use of atomistic simulation techniques allows the examination of the defect energetics, Na-ion diffusion and dopant properties within the crystal. Here, we show that the lowest energy intrinsic defect process is the Na-Ni anti-site. The Na Frenkel, which introduces Na vacancies in the lattice, is found to be the second most favourable defect process and this process is higher in energy only by 0.16 eV than the anti-site defect. Favourable Na-ion diffusion barrier of 0.67 eV in the ab plane indicates that the Na-ion diffusion in this material is relatively fast. Favourable divalent dopant on the Ni site is Co2+ that increases additional Na, leading to high capacity. The formation of Na vacancies can be facilitated by doping Ti4+ on the Ni site. The promising isovalent dopant on the Ni site is Ga3+.

Highlights

In the field of energy storage, a significant amount of research activity has been devoted to Li-ion batteries [1,2,3,4,5,6,7,8,9,10]
As the global distribution of lithium is limited and inhomogeneous, there is a necessity to find an alternative to the lithium ion battery for the next-generation of high capacity energy storage systems, in the hybrid electric vehicles
Rechargeable sodium ion batteries have become promising for the application in large-scale energy storage devices due to the remarkable abundance of sodium on the earth

Summary

Introduction

In the field of energy storage, a significant amount of research activity has been devoted to Li-ion batteries [1,2,3,4,5,6,7,8,9,10]. As the global distribution of lithium is limited and inhomogeneous, there is a necessity to find an alternative to the lithium ion battery for the next-generation of high capacity energy storage systems, in the hybrid electric vehicles. Rechargeable sodium ion batteries have become promising for the application in large-scale energy storage devices due to the remarkable abundance of sodium on the earth. Developing cathode materials exhibiting cheap, safe and high energy density is one of the key steps for constructing promising rechargeable SIBs. A variety of sodium-based cathode materials have been examined experimentally and a limited number of theoretical works have been reported in the literature [4,5,11,12,13,14,15,16,17,18,19,20]. Low potential and large atomic weight of Na lead to the specific energy reduction in the battery [4]

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