Change search
Link to record
Permanent link

Direct link
BETA
Publications (2 of 2) Show all publications
Araujo, R. B., Chakraborty, S., Barpanda, P. & Ahuja, R. (2016). Na2M2(SO4)(3) (M = Fe, Mn, Co and Ni): towards high-voltage sodium battery applications. Physical Chemistry, Chemical Physics - PCCP, 18(14), 9658-9665
Open this publication in new window or tab >>Na2M2(SO4)(3) (M = Fe, Mn, Co and Ni): towards high-voltage sodium battery applications
2016 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 14, p. 9658-9665Article in journal (Refereed) Published
Abstract [en]

Sodium-ion-based batteries have evolved as excellent alternatives to their lithium-ion-based counterparts due to the abundance, uniform geographical distribution and low price of Na resources. In the pursuit of sodium chemistry, recently the alluaudite framework Na2M2(SO4)(3) has been unveiled as a high-voltage sodium insertion system. In this context, the framework of density functional theory has been applied to systematically investigate the crystal structure evolution, density of states and charge transfer with sodium ions insertion, and the corresponding average redox potential, for Na2M2(SO4)(3) (M = Fe, Mn, Co and Ni). It is shown that full removal of sodium atoms from the Fe-based device is not a favorable process due to the 8% volume shrinkage. The imaginary frequencies obtained in the phonon dispersion also reflect this instability and the possible phase transition. This high volume change has not been observed in the cases of the Co- and Ni-based compounds. This is because the redox reaction assumes a different mechanism for each of the compounds investigated. For the polyanion with Fe, the removal of sodium ions induces a charge reorganization at the Fe centers. For the Mn case, the redox process induces a charge reorganization of the Mn centers with a small participation of the oxygen atoms. The Co and Ni compounds present a distinct trend with the redox reaction occurring with a strong participation of the oxygen sublattice, resulting in a very small volume change upon desodiation. Moreover, the average deintercalation potential for each of the compounds has been computed. The implications of our findings have been discussed both from the scientific perspective and in terms of technological aspects.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-185970 (URN)10.1039/c6cp00070c (DOI)000373570200042 ()26996444 (PubMedID)2-s2.0-84962194729 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20160504

Available from: 2016-05-04 Created: 2016-04-29 Last updated: 2017-11-30Bibliographically approved
Araujo, R. B., Chakraborty, S. & Ahuja, R. (2015). Unveiling the charge migration mechanism in Na2O2: implications for sodium-air batteries. Physical Chemistry, Chemical Physics - PCCP, 17(12), 8203-8209
Open this publication in new window or tab >>Unveiling the charge migration mechanism in Na2O2: implications for sodium-air batteries
2015 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 17, no 12, p. 8203-8209Article in journal (Refereed) Published
Abstract [en]

Metal-air batteries have become promising candidates for modern energy storage due to their high theoretical energy density in comparison to other storage devices. The lower overpotential of Na compared with Li makes Na-air batteries more efficient in terms of battery lifetime. Additionally, the abundance of Na over Li is another advantage for Na batteries compared to Li batteries. Na2O2 is one of the main products of sodium-air battery reactions. The efficiency of air cells is always related to the charge transport mechanisms in the formed product. To unveil these diffusion mechanisms in one of the main products of the cell reaction Na-O-2 we systematically investigate the mobility of charge carriers as well as the electronic structural properties of sodium peroxide. The framework of the density functional theory based on hybrid functional approach is used to study the mobility of charge carriers and intrinsic defects in Na2O2. Our calculations reveal that the formation of small electron and hole polarons is preferentially occurring over the delocalized state in the crystal structure of Na2O2. The migration of these small polarons displays activation energies of about 0.92 eV and 0.32 eV for the electron and hole polarons respectively, while the analysis of the charged sodium vacancy mobility reveals an activation energy of about 0.5 eV. These results suggest that the charge transport in sodium peroxide would mainly occur through the diffusion of hole polarons.

National Category
Biochemistry and Molecular Biology Physical Sciences
Identifiers
urn:nbn:se:kth:diva-165244 (URN)10.1039/c4cp05042h (DOI)000351437500069 ()25732774 (PubMedID)2-s2.0-84924870536 (Scopus ID)
Note

QC 20150504

Available from: 2015-05-04 Created: 2015-04-24 Last updated: 2017-12-04Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-6765-2084

Search in DiVA

Show all publications