Waste to Wealth Approach: Customizing Spent LiB Anodes to High Performance Supercapacitor Electrode

Lithium-ion batteries (LiBs) are widely used in various applications because of their high energy density, low self-discharge rate, and portability. The requirements for LiBs continue to increase drastically every year; however, the disposal of spent LIBs is a cumbersome task. To resolve this issue, spent LiB anodes are customized into high-performance supercapacitor (SC) electrodes via supercritical water exfoliation. The specific capacitance of spent LiB anodes (289 F g⁻¹ at 2 A g⁻¹) significantly improved after exfoliation (351 F g⁻¹ at 2 A g⁻¹). Furthermore, the electrochemical performance of the exfoliated LiB anode mushroomed upon the addition of dopamine (as a redox-additive for the first time) with a conventional H₂SO₄ electrolyte. The specific capacitance of the exfoliated LiB anode is incredibly improved after the addition of dopamine with H₂SO₄, from 286 to 571 F g⁻¹ at 4 A g⁻¹. A flexible SC is also fabricated using PVA/H₂SO₄ and dopamine/PVA/H₂SO₄ as the gel electrolyte. The fabricated flexible SC with dopamine/PVA/H₂SO₄ exhibited an enormously high energy density of 44 Wh kg⁻¹ at 700 W kg⁻¹. The increased specific capacitance and energy density of the SC after the addition of dopamine with H₂SO₄ and PVA/H₂SO₄ may be due to the reversible reaction of dopamine to dopamine-o-quinone with H⁺ ions.