Abstract
The ability to achieve high areal capacitance for oxide-based supercapacitor electrodes with high active mass loadings is critical for practical applications. This paper reports the feasibility of the fabrication of Mn3O4-multiwalled carbon nanotube (MWCNT) composites by the new salting-out method, which allows direct particle transfer from an aqueous synthesis medium to a 2-propanol suspension for the fabrication of advanced Mn3O4-MWCNT electrodes for supercapacitors. The electrodes show enhanced capacitive performance at high active mass loading due to reduced particle agglomeration and enhanced mixing of the Mn3O4 particles and conductive MWCNT additives. The strategy is based on the multifunctional properties of octanohydroxamic acid, which is used as a capping and dispersing agent for Mn3O4 synthesis and an extractor for particle transfer to the electrode processing medium. Electrochemical studies show that high areal capacitance is achieved at low electrode resistance. The electrodes with an active mass of 40.1 mg cm−2 show a capacitance of 4.3 F cm−2 at a scan rate of 2 mV s−1. Electron microscopy studies reveal changes in electrode microstructure during charge-discharge cycling, which can explain the increase in capacitance. The salting-out method is promising for the development of advanced nanocomposites for energy storage in supercapacitors.
Highlights
Supercapacitors are currently under development for various energy storage applications [1,2]
Molecules 2021, 26, 296 cation of supercapacitor electrodes, Mn3 O4 particles must be transferred from the aqueous synthesis media to an organic solvent containing a dissolved binder
We explored the salting-out method, which is conceptually different from the particle extraction through a liquid–liquid interface (PELLI) method
Summary
Supercapacitors are currently under development for various energy storage applications [1,2]. Investigations in this research area are focused on the synthesis of advanced electrode materials by different fabrication methods [3,4,5,6,7,8], optimization of electrolytes [9], design of nanocomposites [10,11,12,13], and modeling [14]. Recent studies have highlighted the need for the development of efficient electrodes with high active mass loading and the low mass of passive components [24]. It should be noted that high gravimetric capacitance is achieved only in thin films. The increase in active mass results in poor electrolyte access to the active material and high resistance. The gravimetric capacitance decreases with increasing active mass
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