Waste polyethylene terephthalate-derived organic-inorganic hybrid materials as sustainable dual electrodes for Li-ion batteries

The hybrid Fe-Li₂TP structure is constructed from waste polyethylene terephthalate (w-PET) derived dilithium terephthalate (Li₂TP) and conventional Fe₂O₃ by hydrothermal reaction. It is being studied for both anode and cathode for LIBs. As an anode, it exhibits a reversible capacity of 505 mAh/g after 100th cycle at 1 C-rate with ∼100 % coulombic efficiency (CE). In addition, as a cathode, it shows highly reversible charge/discharge capacities of 107.50/107.52 mAh/g after the 100th cycle at 0.1 C-rate with 100 % CE. Further, in the cathodic studies via galvanostatic intermittent titration technique (GITT), the average lithium diffusion (D_Li+) coefficients are calculated to be 2.96 × 10^-10, 3.89 × 10⁻¹⁰ cm² s⁻¹ and the electrical (µ) mobilities to be 5.86 × 10¹¹ m² V⁻¹ s⁻¹, 1.12 × 10¹¹ m² V⁻¹ s⁻¹ for charge and discharge pulses, respectively. The combined nano-rod and nano-spherical morphologies reduce the diffusion length, and adding 10 % SWCNTs during electrode fabrication enhances the electronic conductivity. This organic–inorganic hybrid strategy of Fe-Li₂TP strongly mitigates the electrode dissolution, reducing the structural strain and preventing electrolyte decomposition at higher voltage. Computational studies show an optimized Fe-Li₂TP structure with a 2.7-fold lower band gap value (1.9040 eV) than the pristine Li₂TP.