Co-Ni-Mn Sulfide Mixed-Phase Composite Electrode Recovered from Spent LIB Black Mass for High-Performance Supercapacitors

This study reports an integrated hydrometallurgical and hydrothermal route that converts NMC-type black mass from spent Li-ion batteries into a mixed cobalt-nickel-manganese sulfide (CNMS) and demonstrates its application as a high-performance positive electrode for asymmetric supercapacitor (ASC). Black mass is leached in 3 M H 2 SO 4 with 10% v/v H 2 O 2 (S/L = 1:50) at room temperature. The dissolved Co, Ni and Mn are co-precipitated as a mixed hydroxide (CNMOH) by pH adjustment and subsequently sulfidized to produce CNMS via thioacetamide-assisted ion exchange in a hydrothermal reactor (180 °C, 12 h). Electrochemical characterization in a three-electrode cell yields an areal capacitance of 1262 mF.cm −2 (CV, 5 mV.s −1 ) and 1103 mF.cm −2 (GCD, 5 mA.cm −2 ). An ASC (CNMS//graphite, 6 M KOH) delivers an areal capacitance of 88.3 mF.cm −2 (5 mV.s −1 ), respectively. This ASC device shows the energy and power density values of 11.06 μWh.cm −2 and 367 μW.cm −2 and retains 80.6% capacitance after 5000 cycles. The combined recovery-to-device approach highlights the feasibility of upcycling the battery black mass into ternary transition metal sulfide. This work provides a practical pathway to couple critical materials recovery with advanced electrochemical energy storage.