Reusing spent graphite through direct electropolymerisation of polypyrrole for sustainable pseudocapacitive electrodes.

Lithium-ion battery recycling is largely focused on metal recovery, while graphite-rich residues remain comparatively undervalued despite their critical-material relevance and intrinsic conductivity. Here, spent graphite recovered from LIB waste was directly upgraded into a pseudocapacitive electrode via polypyrrole electropolymerisation, thereby avoiding high-temperature treatment, complex chemical activation, and expensive active materials. PPy was deposited onto spent graphite from 0.1 M pyrrole solution, producing cauliflower-like conductive coatings with improved electrochemical activity. The electrodes were evaluated by cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy in 1 M H2SO4, demonstrating good electrochemical performance. A symmetric cell was constructed, achieving a specific capacitance of 37.8 F g-1 at 0.5 A g-1, with excellent rate capability and 86.3% capacitance retention after 5000 cycles. This work demonstrates a simple and scalable route for converting graphite-rich battery waste into sustainable pseudocapacitive electrodes for high-power energy-storage applications.