Conversion pseudocapacitance-contributing and robust hetero-nanostructural perovskite KCo_0.54Mn_0.46F₃ nanocrystals anchored on graphene nanosheet anodes for advanced lithium-ion capacitors, batteries and their hybrids

Abstract

The pseudocapacitive conversion mechanism and robust perovskite fluorides/graphene hetero-nanostructures contribute to fast rate capability, high specific capacity and superior stability.

Engineering doping-vacancy double defects and insights into the conversion mechanisms of an Mn–O–F ultrafine nanowire anode for enhanced Li/Na-ion storage and hybrid capacitors

“…4C shows the CV plots of MnF 2 8#-E at a sweep speed of 0.1 mV s À1 , with two weak cathode peaks at 1.64 V and 1.07 V and a sharp cathode peak at 0.52 V in the rst cathode sweep, which may be due to the conversion of Mn-O-F into Mn/LiF/ Li 2 O and the formation of the SEI lms, and the minor anodic peak at 1.17 V can be ascribed to the partial conversion of Mn/ LiF/Li 2 O into MnF 2 /MnO. 14,31,32 In the next two cycles, the cathode peaks shied slightly from 0.56 V to 0.46 V, and the anode peaks shied slightly from 1.18 V to 1.19 V, indicating good reversibility. Fig.…”

“…Moreover, the Na-ion storage capacity in the low potential region also originated from a reversible interfacial Na-ion intercalation reaction within the Mn/NaF matrix as Li-ion intercalation. [31][32][33][34][35] Also, the minor anodic peak at about 1.61 V can be ascribed to the partial conversion of Mn/ NaF into MnF 2 . In the second and third laps, the reduction peaks changed lightly from 0.81 V to 0.72 V, and the oxidation peaks were basically maintained at 1.61 V, indicating good reversibility.…”

“…These peaks are largely owing to the conversion of MnF 2 into Mn/LiF and the formation of solid electrolyte interphase (SEI) lms accompanied with a highly reversible interfacial Li-ion intercalation reaction within the Mn/LiF matrix in the low potential region, respectively. [31][32][33][34][35] Also, the minor anodic peak at 1.01 V can be ascribed to the partial conversion of Mn/LiF into MnF 2 . 31,32 However, the redox peaks were maintained at about 1.01/0.61 V in the subsequent cycles, and it can be seen from the charge-discharge curves that the capacity is basically unchanged in the subsequent cycles except for the much larger specic capacity of the original discharge, indicating that the internal structure is protected aer the formation of the SEI lms, and shows good electrochemical stability.…”

“…31,32 However, the redox peaks were maintained at about 1.01/0.61 V in the subsequent cycles, and it can be seen from the charge-discharge curves that the capacity is basically unchanged in the subsequent cycles except for the much larger specic capacity of the original discharge, indicating that the internal structure is protected aer the formation of the SEI lms, and shows good electrochemical stability. 31,32 Similar changing trends in the redox peaks and charge-discharge platforms can be also found from the CV curves and GCD plots of the other MnF 2 samples, as shown in Fig. S7 and S8.…”

“…The enhanced performance of the Mn-O-F ultrane nanowires with the hetero oxygen doping and uorine vacancies provides an important strategy for the promotion of charge storage capability of Li-ion anode materials. Herein, the initial increase in capacity for the MnF 2 8# and MnF 2 8#-E electrodes may be owing to the formation of continuous conductivity networks via the conversion, reversible reactions of SEI lms and enhanced electroactive sites by the activation of the electrode, 32 while the subsequent decrease in capacity for the MnF 2 8#-E electrode may be owing to the decrease in the electroactive sites by the agglomeration of the amorphous ultrane nanoparticles. The XRD patterns of the electrodes aer cycling (Fig.…”