Abstract
A mesoporous Mn-Co oxide for supercapacitors was derived from a mixed oxalate Mn0.8Co0.2C2O4·nH2O, which was synthesized by a solid-state coordination reaction at room temperature. The synthesized mixed Mn-Co oxalate was decomposed in air at 250°C, resulting in a tetragonal spinel Mn-Co oxide with a primary particle size less than 100 nm. The obtained Mn-Co oxide presents a mesoporous texture with a specific surface area of 120 m2·g﹣1. Electrochemical properties of the Mn-Co oxide electrode were investigated by cyclic voltammetry and galvanostatic charge/discharge in 6 mol·L﹣1 KOH electrolyte. The Mn-Co oxide electrode delivered specific capacitances of 383 and 225 F·g﹣1 at scan rates of 2 and 50 mV·s﹣1, respectively. Subjected to 500 cycles at a current density of 1.34 A·g﹣1, the symmetrical Mn-Co oxide capacitor showed specific capacitance of 179 F·g﹣1, still retaining ~85% of its initial capacitance. The obtained Mn-Co oxide material showed good capacitive performance, which was promising for supercapacitor applications.
Highlights
Electrochemical supercapacitors possess the unique energy-storage performance, such as greater power density and longer cycle life than secondary batteries, as well as higher energy density than conventional capacitors [1], showing great potential to be used in the areas of hybrid power sources, peak power sources, backup power storage, lightweight electronic fuses, starting power of fuel cells [2,3]
The supercapacitors can be classified into two categories: electrical-double-layer capacitors (EDLCs), which build up electrical charge at the electrode/electrolyte interface [4,5], and pseudocapacitors, which are based on reversible faradic redox reactions at the interfaces at certain potentials [6,7,8,9,10]
The electrodes for electrochemical measurements consisted of the prepared Mn-Co oxide, acetylene black (AB) and polytetrafluoroethylene (PTFE), whose weight ratio was 75:20:5
Summary
Electrochemical supercapacitors possess the unique energy-storage performance, such as greater power density and longer cycle life than secondary batteries, as well as higher energy density than conventional capacitors [1], showing great potential to be used in the areas of hybrid power sources, peak power sources, backup power storage, lightweight electronic fuses, starting power of fuel cells [2,3]. Amorphous hydrated ruthenium oxide has been demonstrated to be an excellent pseudocapacitor material, which exhibits a high conductivity, good electrochemical stability, and a large specific capacitance (SC) of 720 760 F·g 1 [21]. The electrode materials of the cheaper transition metal oxides exhibit remarkable capacitive nature, delivering a considerable SC. The resistivity and the equivalent series resistance (ESR) of these cheaper transition metal oxides are very large, which greatly limits their capacity and power density available. It is reported that mixed oxide composites exhibit superior capacitive performance to single transition metal oxides. The obtained Mn-Co oxide shows excellent capacitive performance in terms of specific capacitance (SC), power capability and cycling stability, which is promising for supercapacitor applications
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