Abstract
Porous Mn2O3 microspheres have been synthesized and in-situ coated with amorphous carbon to form hierarchical C@Mn2O3 microspheres by first producing MnCO3 microspheres in solvothermal reactions, and then annealing at 500 °C. The self-assembly growth of MnCO3 microspheres can generate hollow structures inside each of the particles, which can act as micro-reservoirs to store biomass-glycerol for generating amorphous carbon onto the surfaces of Mn2O3 nanorods consisting of microspheres. The C@Mn2O3 microspheres, prepared at 500 °C, exhibit highly enhanced pseudocapacitive performances when compared to the particles after annealed at 400 °C and 600 °C. Specifically, the C@Mn2O3 microspheres prepared at 500 °C show high specific capacitances of 383.87 F g−1 at current density of 0.5 A g−1, and excellent cycling stability of 90.47% of its initial value after cycling for 5000 times. The asymmetric supercapacitors assembled with C@Mn2O3 microspheres after annealed at 500 °C and activated carbon (AC) show an energy density of up to 77.8 Wh kg−1 at power density of 500.00 W kg−1, and a maximum power density of 20.14 kW kg−1 at energy density of 46.8 Wh kg−1. We can attribute the enhanced electrochemical performances of the materials to their three-dimensional (3D) hierarchical structure in-situ coated with carbon.
Highlights
Supercapacitors, as old brothers of batteries, have attracted considerable attentions in the last decade, because of the dramatic advances concerned with materials science and the theories of storing charges [1,2,3,4]
The carbon coatings on the surfaces of the microspheres can be attributed to their high yield of more than 100%
The results reveal that the carbon coatings on the surfaces of the C@Mn2O3 microspheres should be produced during their annealing process instead of in the reactions
Summary
Supercapacitors, as old brothers of batteries, have attracted considerable attentions in the last decade, because of the dramatic advances concerned with materials science and the theories of storing charges [1,2,3,4]. Our experimental results verify that porous and uniform Mn2O3 microspheres that are coated with amorphous carbon can be produced on a large scale by annealing MnCO3 precursors with biomass glycerol in-situ encapsulated inside the voids of the particles. Our experimental results verify that porous and uniform Mn2O3 microspheres that are coated with amorphous carbon can be pNraondomuacteerdialso20n17,a7, 4la09rge scale by annealing MnCO3 precursors with biomass glycerol in7-soiftu encapsulated inside the voids of the particles. TToo ffuurrtthheerr eevvaalluuaattee tthhee eelleeccttrroocchheemmiiccaall ppeerrffoorrmmaanncceess ooff tthhee aassyymmmmeettrriicc cceellllss,, RRaaggoonnee pplloott (cd2(b7FFa07eyili.n.ggc18fsuu4uoWilrrltkalyeeoWth7ew7odfkf)fkig)nrbg−7egry−l7e11aE.lfaat8aoiqtttvliulaWpevonaoetwthoweioitntnoekhnerggesrtd−ghEc(1e4yoeqna)rudtrcsaeaeiontpstnryidporoseoowin(tsnf5yspe)d5r.oo(0i4nTnf0d)gdh4.e0a6eien0nn.n8asdgWeisWtry(yeg5kmnhy)go.em(k−frTEgg1eh)5y−tae0a1r.nn0i(aTc.dEds0hc)y0paeamaopmeWnwmalaedcecexikrtttiporgrm(ooPir−c1suwc)hcmdeaeaexnerpmhnpda(sioiPbcicwati)iaitteolemdtsrprhesoaedenfxreeshftixnihomithsgreiieiumhbtdsymeieatsovonttfifpchcee2oetensh0wseh.eow1riefgg4drahyhkseidevWdecseraietcnalnkecerssusngcitihl−etyawyir1tcgeaoaoaydsflft microspheres are superior to the Mn2O3 materials reported so far [34], and the energy density of the device assembled with C@Mn2O5-500 is much higher in comparison with that of devices made with Mn-based electrode materials such as MnO2/AC [13], MnO2/GO [35,36], Mn3O4/Carbon-aerogel [12], MnOOH/GO [25], MnO2/Carbon-nanofiber [16], MnO2/AC [37], MnO2/Onion-like-carbon [15], MnO2/CNT [20,38], and Mn3O4/RGO [28] in aqueous electrolyte solutions. FFiigguurree 7.7E. leEctlreoccthreomchiceaml picearlforpmearnfocerms oafnCc@esMno2fO3C-5@00M/n/2aOct3i-v5e0c0a/r/abcotniv(Ae Cc)aarsbyomnme(tAricCs)upaesrycampmaceittorrisc. (sau)pCeyrccalipcaVcoitlotarsm. m(ao) gCryamclic(CVVo)ltcaumrvmeosgartadmiff(eCrVen)tcsucravnesraatet sd; i(fbfe)rcehnatrsgcea/ndrisactheas,rg(be)ccuhrvaergsea/tddisicfhfearregnet ccuurrrveenst daetndsiitfiefesr; e(cn)tthceusrpreencitficdceanpsaitciietasn, c(ecs) atthdeiffsepreenctifcicurcreanptadceitnasnitcieess; (adt) dcyifcfleersetnabt ilcituyrraenndtCdoeunlosmitibeisc, e(dff)iciceyncclye isntaKbOilHityelaecntdrolCytoeuolof m6 Mbi;c(ee)ffNicyieqnucisyt iimnpKedOaHnceelsepcetcrtorluymte; aonfd6(fM) R,a(geo)nNe pylqoutsi.st impedance spectrum, and (f) Ragone plots
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