Enhanced Oxygen Evolution Reaction by Cobalt Oxalate Recovered From Spent Lithium‐Ion Battery and Performance of Re‐Synthesized LiCoO 2

ABSTRACT The development of an efficient and eco‐friendly spent lithium‐ion batteries (LIBs) recycling strategy is vital for economic and environmental sustainability. This study reports a green, efficient and economic method to convert the cathode portion of spent LIB (LiCoO 2 ) into a high‐performance nonprecious Co‐oxalate (CoC 2 O 4 ·2H 2 O) electrocatalyst for the oxygen evolution reaction (OER). Here, LiCoO 2 collected from the spent LIB cathode was leached in oxalic acid and gallic acid (200:20 mM) mixture at 80°C using a solid‐to‐liquid ratio of 2 g/L for 1 h. Soon after the dissolution of Co and Li, in situ precipitation of CoC 2 O 4 2H 2 O was observed in the reaction mixture and soluble Li was precipitated as Li 2 CO 3 and LiHC 2 O 4 H 2 O when stoichiometric excess of Na 2 CO 3 and oxalic acid were added, respectively. The recovered CoC 2 O 4 ·2H 2 O deposited on stainless steel plate was utilized as an anode for electrochemical OER. It showed an overpotential of 320 mV at 10 mA cm −2 , a low Tafel slope (49 mV dec −1 ) and stable performance over 12 h. Furthermore, the battery grade LiCoO 2 was re‐synthesized using the stoichiometric amounts of LiHC 2 O 4 H 2 O and CoC 2 O 4 2H 2 O. The re‐synthesized LiCoO 2 showed almost 100% coulombic efficiency with a minimal capacity loss. Thus, we have demonstrated an effective recovery and reuse of cathode material for energy devices.