Unique Structure-Induced Magnetic and Electrochemical Activity in Nanostructured Transition Metal Tellurates Co<sub>1 – <i>x</i></sub>Ni<i><sub>x</sub></i>TeO<sub>4</sub> (<i>x</i> = 0, 0.5, and 1)
Akhilesh Kumar Patel, Manas Ranjan Panda, Ekta Rani, Harishchandra Singh, S. Shanmukharao Samatham, N. Abharana, Sambhu Nath Jha, D. Bhattacharyya, K. G. Suresh, Sagar Mitra
Abstract
The emergence of cutting-edge nanomaterials with rational design, primarily with a structure-driven functionality, is a prerequisite for achieving advancement in current energy scenarios. This report presents facile sol–gel-grown, first-of-its-kind, nanostructured transition metal tellurates Co1 – xNixTeO4 (x = 0, 0.5, and 1). These are a class of promising magnetic and energy storage materials. Along with electronic structure signatures of individual nanocrystals through electron energy loss spectroscopy, microstructural and high-resolution synchrotron X-ray diffraction analysis results in a new structural model, which further sheds light on the structure-driven performances of these tellurates. Antiferromagnetic interactions observed at ∼48, 58, and 76 K for x = 0, 0.5, and 1, respectively, surpass numerous antiferromagnets. The robust electrochemical activity of NiTeO4 against Li metal shows a high reversible specific capacity of ∼1271 mA h g–1 in the first discharge cycle, with 80% capacity retention over long-term cycles. Thorough ex situ X-ray absorption fine-structure spectroscopy and transmission electron microscopy investigations performed on several charging/discharging cycled electrodes establish a conversion-based battery reaction mechanism. The resulting anode, thus, displays unprecedentedly high stability in comparison to existing transition metal-based anode materials for Li-ion batteries. The observed outcomes are further understood to stem from different degrees of the Jahn–Teller-like z-out and z-in distortion in the respective d orbitals of Co2+ and Ni2+.