Suppressing early capacitance fade of electrochemical capacitors with water-in-salt electrolytes

Autor(es)

Martins, Vitor L. ^[1] ; Mantovi, Primaggio Silva ^[1] ; Torresi, Roberto M. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Quim, Dept Quim Fundamental, Ave Prof Lineu Prestes 748, BR-0550800 Sao Paulo, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Electrochimica Acta; v. 372, MAR 10 2021.
• Citações Web of Science: 0

Resumo

The use of water-in-salt electrolytes (WiSEs) in electrochemical capacitors is an interesting alternative to state-of-the-art electrolytes based on organic solvents. However, making use of their wide electrochemical stability in electrochemical capacitors has been challenging, as shown in battery materials. In this work, we used three concentrations of LiTf2N in water (7, 15 and 21 mol kg(-1)) with activated carbon, and the determination of the maximum operating voltage showed stability up to 2.2, 2.4 and 2.6 V, respectively. This determination suggested positive/negative-electrode mass balances of 2.1, 1.5 and 1.2, but the experiments showed that the cycle life of devices using WiSEs of 15 and 21 mol kg(-1) can be improved. Thus, we find that increasing the amount of active material in the positive electrode gave higher capacitance retention over cycling. With the optimization for a longer cycle life, the observed capacitance retentions for the devices with WiSEs of 7, 15 and 21 mol kg(-1) were 97%, 70% and near 100%, respectively, after 10000 cycles. The higher amount of active material in the positive electrode penalized the energy-power performance, but the higher electrochemical stability compensated for it, and WiSEs of 7, 15 and 21 mol kg(-1) stored 15, 16 and 21 W h kg(-1) when they operated at 0.1 A g(-1). (C) 2021 Elsevier Ltd. All rights reserved. (AU)

• Processo FAPESP: 13/22748-7 - Desenvolvimento de Capacitores Eletroquímicos de Alto Desempenho, Baseado em Grafeno e Líquidos Iônicos.
• Beneficiário: Vitor Leite Martins
• Linha de fomento: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 18/19459-7 - Misturas de líquidos iônicos para otimização de supercapacitores
• Beneficiário: Primaggio Silva Mantovi
• Linha de fomento: Bolsas no Brasil - Iniciação Científica
• Processo FAPESP: 15/26308-7 - Otimização das propriedades físico-químicas de materiais nano-estruturados e suas aplicações em reconhecimento molecular, catálise e conversão/armazenamento de energia
• Beneficiário: Roberto Manuel Torresi
• Linha de fomento: Auxílio à Pesquisa - Temático