Local Structure Distortion in Mn, Zn Doped Cu₂V₂O₇: Supercapacitor Performance and Emergent Spin-Phonon Coupling

Supercapacitors are rapidly gaining attention as next-generation energy storage devices due to their superior power and energy densities. This study pioneers the investigation of Mn/Zn co-doping in α-Cu₂V₂O₇ (CVO) to enhance its performance as a supercapacitor electrode material. Structural and local Structural properties of Mn/Zn co-doped CVO have been investigated through X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), and X-ray Absorption Spectroscopy (XAS), revealing significant distortions that enhance supercapacitor performance. The optimized sample demonstrates a remarkable specific capacitance of 1950.95 Fg, energy density of 97.54 Whkg, and enhanced capacitive retention, attributed to the unique Cu coordination environment and improved charge transfer kinetics. Temperature-dependent Raman spectroscopy unveils spin-phonon coupling (SPC), particularly in VO₄ stretching modes, supported by magnetic measurements that shows a reduction in the Néel temperature and the emergence of zero field-cooled (ZFC) exchange bias (EB). This work is the first to report the impact of local structure distortion on both supercapacitor performance and SPC in CVO, offering a novel strategy for developing high-performance energy storage materials with spintronics potential. In addition, the assembled symmetric optimized supercapacitor shows a high energy density of 93.32 Whkg and excellent cycling stability. A prototype device incorporating the optimized CVO successfully powers eight commercial LED bulbs, demonstrating its practical application potential.