Composite Mn–Co electrode materials for supercapacitors: why the precursor's morphology matters!

Abstract

In the energy storage field, an electrode material must possess both good ionic and electronic conductivities to perform well, especially when high power is needed. In this context, the development...

Incorporation of Fe3+ into MnO2 birnessite for enhanced energy storage: impact on the structure and the charge storage mechanisms

“…32,[44][45][46][47] Nevertheless, the particle size in this series of material remains signicantly larger than the typical range of 5 to 100 nm observed for birnessites obtained through "chimie douce" methods. 27,48 Finally, EDX mappings performed on the series of samples conrmed the homogeneous distribution of Fe throughout the entire sample, as illustrated Fig. 3f for the d-Mn 0.8 Fe 0.2 O 2 sample.…”

“…23,24 Another interesting approach to boost the electronic conductivity is the elaboration of composites-nanocomposites MnO 2 / conductive metal 25 or MnO 2 /transition metal oxides. 26,27 Although these approaches improve overall conductivity, the intrinsic electronic conductivity of the birnessite phase remains unchanged and the performance of composite electrode materials heavily relies on achieving a homogeneous distribution between the electronic conductive phase and MnO 2 . 27 To overcome this issue, it is possible to incorporate heteroatom into birnessite to change its electronic structure and reduce its electronic band gap.…”

“…26,27 Although these approaches improve overall conductivity, the intrinsic electronic conductivity of the birnessite phase remains unchanged and the performance of composite electrode materials heavily relies on achieving a homogeneous distribution between the electronic conductive phase and MnO 2 . 27 To overcome this issue, it is possible to incorporate heteroatom into birnessite to change its electronic structure and reduce its electronic band gap. [28][29][30][31] For instance, Liu et al have demonstrated through rst principle calculations that a partial substitution of Mn 3+/4+ by Fe 3+ in the metal oxide layer reduces the electronic band gap from 1.03 eV to 0.62 eV (for 33 mol% of substitution) and enhances the specic capacity when compared to d-MnO 2 at equivalent charging/discharging rates.…”

Manganese–cobalt geomimetic materials for supercapacitor electrode

“…The results obtained in the present work can also to be compared with those of Tang et al and Invernizzi et al, whose goal was to combine the pseudocapacitive property of birnessite with cobalt oxyhydroxide phases, which are known to be more conductive. 18,19 A "nano-architectural" approach was adopted in this case, which consisted of going through exfoliation/restacking steps of lamellar oxides. 19,58 The different oxide layers are then considered to be elementary bricks, which are then assembled to obtain nano-composites.…”

“…15,16 With the aim of developing high-performance electrodes for supercapacitors, previous works in our laboratory have focused on combining the pseudocapacitive properties of lamellar manganese phases such as birnessite and the faradaic and electronic conduction properties of lamellar cobalt oxyhydroxides containing Co 4+ ions 17 in a single material via an original synthesis strategy involving exfoliation and restacking from lamellar manganese birnessite and β(III) or γ cobalt oxyhydroxides. 18,19 Tang et al obtained nanocomposites made of assembled Mn-and Co-based building blocks. 19 Electrochemical study of these nanocomposites showed an efficient synergy effect between the Mn and Co blocks, with Co slabs having a beneficial effect on capacity, especially at high rate.…”