Energy storage in highly concentrated electrolyte: an interfacial study

Author(s)

Thiago Takeshi Obana

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ)
• Defense date: 2021-09-30

Examining board members

Roberto Manuel Torresi; Lucio Angnes; Germano Tremiliosi Filho; Hudson Giovani Zanin

• Advisor: Roberto Manuel Torresi

Abstract

The current energy and environmental scenario has led society to rethink new energy sources, as an alternative to fossil fuels. Moreover, there is the demand for new modes of energy storage, which have high energy and power densities. In this sense, the suitable choice of electrode materials (positive/negative) and electrolyte is critical. In this context, electrochemical capacitors (EC) are included. Unlike batteries, such devices retain energy from the electrostatic charge/discharge of the electrical double layer (electrode/solution) and, in some cases, from fast faradaic or pseudo-capacitive processes. Another difference between EC and batteries relies on the amount of stored energy (energy density) and the average power density of each device. While capacitors display a low energy density and a high power density; the batteries, on the other hand, are capable of providing medium power density. However, for batteries and especially for capacitors, electrolyte remains a critical choice, as organics ones have been preferred. Given the need for safe and environmentally correct options, it is advisable to use aqueous electrolytes. Despite the narrow electrochemical window limited to ~1.0 V, aqueous electrolytes are preferred. In this way, the so-called Waterin-Salt Electrolyte (WiSE), which consists in highly concentrated aqueous electrolytes, emerge as an interesting alternative given the expansion of the electrochemical window of some systems beyond 2.0 V. Thus, in the present study, using conductive polymers, such as polypyrrole and PEDOT (polyethylenedioxythiophene), copperbased Prussian blue analogue and carbonaceous materials as active electrode materials, electrochemical capacitors and hybrid devices with electrochemical windows greater than 2.0 V, operating on WiSE, were obtained. Furthermore, using the electrochemical crystal quartz microbalance with dissipation (EQCM-D), these interfaces in WiSE and in diluted electrolyte were studied. (AU)

• FAPESP's process: 17/10046-9 - Energy storage devices with high capacity and power
• Grantee: Thiago Takeshi Obana
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)