Contents lists available at ScienceDirect Journal of Energy Storage journal homepage: www.elsevier.com/locate/est Combustionsynthesisofbattery-typepositiveelectrodesforrobustaqueous hybrid supercapacitor A. Bello a,b, ⁎ ,D.M.Sanni a,c , S.A. Adeniji a,c ,V.Anye b,d ,K.Orisekeh b ,M.Kigozi b ,R.Koech b a Department of Theoretical and Applied Physics, African University of Science and Technology (AUST), Abuja, Nigeria b Department of Materials Science and Engineering, African University of Science and Technology (AUST), Abuja, Nigeria c Department of Physics, Nile University of Nigeria, Plot 681, Cadastral Zone C, Abuja, Nigeria d Department of Electrical/Electronics, Nile University of Nigeria, Plot 681, Cadastral Zone C, Abuja, Nigeria ARTICLEINFO Keywords: Electric energy storage Supercapacitors Double layer capacitors Activated carbon LiMnO Electric cars ABSTRACT Producingmaterialswithsuitablefeaturesincludingrobust,andhighelectricalconductivityfortherealization ofexcellentelectrochemicalperformanceforsupercapacitordevicesremainsagreatchallenge.Inthisregard,we optimize and used the combustion synthesis technique assisted with urea for the production of a positive electrode based on battery type lithium manganese oxide (LiMnO) and activated carbon as negative electrode materials for high voltage hybrid devices in aqueous electrolytes. The samples were analyzed with X-ray dif- fraction,Ramanspectroscopy,andscanningelectronmicroscopy.Thestructuralpropertiesofthematerialwere studiedandhybriddevicesfabricatedpresentaspecifccapacitanceof65Fg −1 and78Fg −1 ,at0.5Ag −1 in 1MLi 2 SO 4 and1MNa 2 SO 4 respectively,withlong-termstabilityaftercontinuouscycling.Theseresultshows thatthisstrategycanrevolutionizenewwaystothesynthesisofaplethoraofmaterialsforhighvoltageenergy storage applications. 1. Introduction The systematic and continuous development of hybrid functional materialshasresultedintremendousimprovementintheperformance of electrochemical devices such as batteries and supercapacitors (SCs) applications in mobile technologies and electric vehicles (EVs). In the traditional gasoline vehicles, a substantial amount of energy is lost during braking or during periodic acceleration and deceleration. Consequently, the recovery of this energy through regenerative breaking is an efective method to improve the driving range and as such can only be accomplished by EVs. This has become popular and widelyaccepted,anditisprojectedthattheywillplayamajorfunction inthenewrevolutionofcarsby2038 [1].Generally,EVshavebecome acceptablecommercially,andtheyemploytwosimilartypesofelectric energystoragedevicestosatisfyanefectivedesignofthesystem.These storagesystemsarebatteriesthatstoreenergyfromachemicalreaction and SCs that store energy using a surface phenomenon of adsorption (electrostatic interactions). Recently, SCs have elicited vast research interest as high power devices to complement batteries due to their fascinating properties which include fast recharge capability, high powerdensity,andlongcyclelife [2].Nevertheless,theyhaveimposed somechallengessuchaslowenergydensitiesthatneedstoaddressed,if they are to replace or complement batteries that employ chemical re- actions for increased driving mileage in EVs. The specifc energy is proportionaltothespecifccapacitanceandtothesquareofthevoltage (E =0.5 CV 2 )[3,4]whichisusuallyascertainedbythestabilityofthe electrolyte and the catalytic activity of the active materials used [5]. The use of aqueous electrolytes in SCs has been widely studied, and havethehighestconductivityincontrasttothenon-aqueouselectrolyte such as the organic electrolytes and ionic liquids. They are low cost, safe, environmentally friendly and require less packaging and a much easier option for potential laboratory testing and more desirable from an industrial and commercial stand point [6]. However, aqueous elec- trolytes have voltage limitation to 1.23 V due to thermodynamic dis- sociation of water in hydrogen (H 2 )andoxygen(O 2 ) beyond this vol- tage. Hydrogel electrolytes are also developed for SCs due to their cap- abilitytofulflldualrolesofelectrolyteandseparator.Theyareswollen polymernetworkswithlargeamountsofwaterabsorbed,whichmakes high ionic conductivity and stability against electrolyte leakage pos- sible. For example, a highly fexible/soft yet device-level dynamically super-tough supercapacitor based on the highly efective energy dis- sipationofadualcross-linkedhydrogelelectrolytewasreportedbyLiu et al. [7]. The hydrogel matrix contained a covalently cross-linked https://doi.org/10.1016/j.est.2019.101160 Received 24 October 2019; Received in revised form 12 December 2019; Accepted 16 December 2019 ⁎ Corresponding author at: Department of Theoretical and Applied Physics, African University of Science and Technology (AUST), Abuja, Nigeria. E-mail address: abello@aust.edu.ng (A. Bello). Journal of Energy Storage 27 (2020) 101160 2352-152X/ © 2019 Elsevier Ltd. All rights reserved. T