Unique structure-induced magnetic and electrochemical activity in nanostructured transition metal tellurates Co_{1 - X}Ni _xTeO₄(x = 0, 0.5, and 1)

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+.