a Recently, several excellent SO4-based polyanion cathodes for Na-ion batteries (NIBs) were exploited, e.g. Na2+2xM2-x(SO4)3 (M=Fe and Mn), which can make the NIBs competitive with the state-of-the-art Li-ion batteries (LIBs). To search for more excellent SO4-based materials for NIBs, we studied the Na2SO4-MnSO4 system and isolated a new compound Na2Mn3(SO4)4, which crystallizes in orthorhombic space group Cmc21 with a=14.8307(18) Å, b=9.9107(18)Å, c = 8.6845(12)Å, and Z=4. The structure has the tunnels for migration of Na + ions, which can be confirmed by the BVS maps. The impedance studies further demonstrated the mobility of Na + ions. A high redox potential with the value of 4.48V was obtained using the density functional theory (DFT) method based on the ab initio calculations. Additionally, magnetic test, infrared spectra (IR), and differential scanning calorimeter (DSC) were also employed for the characterization of the material. 28 Almost at the same time, Marinova et al also reported that Na 2+σ Mn 2-σ/2 (SO 4 ) 3 has electrochemical activity in the lithium ions cell. 29 To search for more excellent SO 4 -based insertion materials for NIBs, We studied the Na 2 SO 4 -MnSO 4 system and isolated another new compound Na 2 Mn 3 (SO 4 ) 4 . Herein, we report the synthesis (containing crystal growth), structure, magnetic properties and conductivity of the title compound. In addition, we also calculated the Na + ions diffusional pathway and the redox potential.
The crystals of the title compound have been grown in molten salt media. Single-crystal X-ray diffraction experiment revealed that the compound crystallizes in an orthorhombic space group Pbcn (no. 60) with cell parameters: a = 5.1023(10) Å, b = 19.717(4) Å, c = 12.557(3) Å, and Z = 4. The structure of Li5CsMn(P2O7)2 consists of one-dimensional manganese pyrophosphate chains [MnP4O14]∞ interleaved with Cs(+) and Li(+) cations. A pseudo-two-dimensional layer [CsMnP4O14]∞ parallel to the ab plane is made up of [MnP4O14]∞ chains and Cs-O polyhedra through sharing the oxygen atoms. The three crystallographically distinct Li atoms are all located in the interlayered space to form a 'lithium hamburger' structure. Magnetic studies demonstrated that the compound shows paramagnetic behavior. DSC and XRD investigations revealed that the compound melts congruently. AC impedance studies show that the conductivity is 1.3 × 10(-5) S cm(-1) at 573 K and the activation energy is 0.42 eV. In addition, Li ion diffusional pathways were obtained using the bond valence map.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.