Refurbished zinc manganese oxides from waste batteries as a supercapacitor asymmetric cell: A second life to battery waste

Alkaline Zn/C batteries are major market players in the portable battery sector that produce an overwhelming amount of waste which is a major cause of soil contamination. These batteries, however, contain metal compounds of relevance, whose recycling enables an important source of raw materials for new electrochemical energy storage devices. However, novel recycling solutions require the development of simple pathways to deliver ready-to-use active materials for immediate application in energy storage systems, thus contributing towards waste revalorization and circular economy development. In this work, an asymmetric supercapacitor cell assembled with electrodes made of recycled Zinc–Manganese oxide and commercial carbon YP50, was tested in NaSO electrolyte. The results evidenced an exceptional cycling stability over 5000 cycles with 91% long-term capacitance retention, a high capacitance of 12.9 F/g (1 A/g) and a power density of 4.12 kW/kg (10 A/g), with 88% high-rate capability. The electrodes made with the recovered materials were fully characterized using 3D electrochemical impedance spectroscopy (EIS) mapping to detail the mechanisms governing the electrochemical response of the cell. This approach evidenced a surface-based pseudocapacitive mechanism where the charging process dictates the overall performance of the cell. The excellent performance of the recycled materials will certainly encourage circular economy and future waste-recovery initiatives, aiding in the sustainable development of future energy storage materials.

The authors acknowledge Centro de Química Estrutural Research Unit funding by Fundaç˜ao para a Ciˆ encia e Tecnologia (FCT): projects UIDB/00100/2020,theInstituto deCiˆ encias Moleculares Research Unit, funding by Fundaç˜ ao para a Ciˆ encia e Tecnologia (FCT): project LA/P/ 0056/2020. M.A. Almeida acknowledges the PhD scholarship funding by Fundaç˜ ao para a Ciˆ encia e Tecnologia (FCT): through the Heal-Cap project: Self-healing electrodes for Hybrid Supercapacitors: A new path to enable electrochemical energy storage, DOI 10.54499/PTDC/ QUI-ELT/2075/2020. The authors also acknowledge the financial support from the project “NGS–NewGenerationStorage”[C644936001-00000045],financedby PRR–PlanodeRecuperaç˜ ao e Resiliˆ encia under the Next Generation EU from the European Union, and the financial support from FCT for the Corkcap project: 2022.05187.PTDC. P. Ar´ evalo-Cid would like to acknowledge FCT for funding through CEECIND/01965/2018.