Sodium Interaction with Disodium Terephthalate Molecule: an Ab Initio Study
- PDF / 487,956 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 53 Downloads / 1,039 Views
Sodium Interaction with Disodium Terephthalate Molecule: an Ab Initio Study Mahasin Alam Sk1 and Sergei Manzhos1* Department of Mechanical Engineering, National University of Singapore, Block EA #07-08, 9 Engineering Drive 1, Singapore 117576, Singapore *E-mail: [email protected]
1
ABSTRACT Disodium terephthalate (Na2TP), which is a disodium salt of terephthalic acid, is very promising organic electrode material for Na-ion batteries. We present an ab initio study of Na binding mechanism with Na2TP molecule. Specially, we provide the interaction energy of Na atom(s), effect of Na concentration on interaction energy, electronic properties of clean and Na attached Na2TP, and Na binding mechanism with Na2TP. We show that up to eight Na atoms can be attached to a single Na2TP molecule. The interaction energy of Na atoms varies from -0.79 to -0.66 eV with attachment of one to eight Na atoms. The adsorbed Na atom interacts with O atoms of carboxylate group and Na atoms of the salt molecule. The interaction between adsorbed Na and C atoms of the molecule is found to be not important for Na bindings. Attachment of a single Na atom generates a singly occupied orbital which becomes doubly occupied with attachment of second Na atoms. Attachment of more than two Na atoms leads to electron occupation of bonding orbitals formed between Na atoms and the carboxylate groups. INTRODUCTION In the field of electrochemical energy storage, organic materials have attracted the interest of researchers due to high theoretical capacities of organic materials, potentially lowcost, recyclability, tuning of redox potential in a wide range, abundant resources from renewable natural products or biomass. The organic materials considered as electrodes for batteries include organosulfur, organic free radical, organic carbonyl and layered organic compounds, conducting and non-conjugated redox polymers1-7. Carboxylate functional groups containing small organic molecules8-9 are attractive electrode materials with tunable physical and electrochemical properties. Zhao et al.10 have demonstrated the use of organic materials (disodium terephthalate: Na2TP) as anode for Na-ion batteries. Na2TP is a disodium salt of terephthalic acid which is very promising organic electrode material with reported Na storage capacities of up to two Na atoms per molecule11. It combines ease of synthesis, environment friendliness and low cost. The terephthalic acid can be produced from recycling of polyethylene terephthalate plastic or oxidation of p-xylene8. The Na storage capacities and anode voltage of Na2TP can be manipulated by simple chemical modifications11-12. To improve the Na storage capacities of Na2TP and to design the new electrode materials based on Na2TP, it is necessary to understand the structural and electronic properties and Na binding mechanism of this molecule. Here, we have investigated the structural and electronic properties of Na2TP molecule as well as the mechanism of interactions with sodium (Na) atoms. Specifically, we study the possibility of at
Data Loading...
