High-Performance All-Solid-State Supercapacitor Based on the Assembly of Graphene and Manganese(II) Phosphate Nanosheets

Abstract

Manganese phosphate nanosheets (Mn3(PO4)2·3H2O NSs) with ∼2 nm thickness were prepared by exfoliating the bulk material in dimethylformamide (DMF) under ultrasonication. They can spontaneously form face-to-face stacked assemblies with exfoliated graphene NSs in DMF. The assemblied Mn3(PO4)2·3H2O and graphene NSs at the mass ratio of 1:10 (M1G10) revealed a specific capacitance of 2086 F g–1 at 1 mV s–1. These M1G10 assemblies were used to fabricate all-solid-state supercapacitor (M1G10-ASSS) on the basis of PVA/KOH solid polymer electrolytes, which exhibited a specific capacitance of 152 F g–1 (or 40 mF cm–2) at 0.5 A g–1, an energy density of 0.17 μWh cm–2 at 0.5 A g–1 (1.3 A m–2) and a power density of 46 μW cm–2 at 2 A g–1 (5.3 A m–2). M1G10-ASSS also showed excellent cycling stability and nearly 100% capacitance retention was achieved after 2000 galvanostatic charge–discharge cycles at 2 A g–1. Such extraordinary properties were attributed to the synergistic effect of high pseudocapacitance of Mn3(PO4)2·3H2O NSs, high conductivity and surface areas of graphene NSs.

Three-dimensional crisscross porous manganese oxide/carbon composite networks for high performance supercapacitor electrodes

“…For MnO x /C composites, the initial potential drops (iR drops) is about 20 mV at the beginning of the discharge curve, which means smaller bulk solution resistance and better conductivity than the 54 mV iR drop of pristine MnO x . The deviation to linearity of the curves implies that the capacitance is mainly associated with pseudocapacitance [32], which is in keeping with the redox reaction of MnO x based on the CV curves. The longer the discharge time of MnO x /C is, the better the capacitance performance displays.…”

Synthesis, structural and electrochemical properties of sodium nickel phosphate for energy storage devices

“…10d. [14][15][16] This behaviour corresponds to an adsorption/desorption mechanism of OH − ions from the NaOH electrolyte. However, for the positive electrode NaNiPO 4 , a distinct pair of redox peaks which is a deviation from the box shaped curve has occurred.…”

“…Next to the oxides and hydroxides, transition metal phosphates and molybdates offer excellent performance in terms of structural stability, energy efficiency, safety and environmental inertness. [14][15][16] The ordered olivine structure, with general formula LiMPO 4 (M = Ni, Fe, Co or Mn) has been extensively studied as a cathode material in battery systems. These compounds contain tetrahedral anion structure units (XO 4 ) n− with strong covalent bonding, generating oxygen octahedral sites occupied by other metal ions.…”

Metal Phosphides and Phosphates‐based Electrodes for Electrochemical Supercapacitors

“…For example, cobalt phosphate Co 3 (PO 4 ) 2 nanoflakes, Co 3 (PO 4 ) 2 ·8H 2 O micro‐flowers, and Co 3 P 2 O 8 ·8H 2 O particles were synthesized by the precipitation processes. Other metal phosphates included nickel phosphates and manganese phosphates . Sonochemistry involves the application of ultrasound to chemical reactions and processes, where the ultrasound helps tune nanoparticles with controllable morphologies .…”

“…By comparison, the electrochemical properties of these manganese and vanadium phosphates are still relatively poor, where the poor conductivity and strong aggregation propensity are the critical challenges that can restrict their applications . Two approaches have been adopted to solve these problems: i) developing a proper hybrid‐type structure with a conducting material, such as graphene, which is not only able to provide conductive paths and avoid aggregation, also contribute to improving the cycling stability, ii) fabricating specific nanostructures, such as nanosheets, by exfoliation of the layered materials.…”