Nanohybrid Of Graphene Oxide And Manganese Dioxide As An Anode Material For High-Performance Lithium-ion Batteries

In a constant scuffle to advance the progress of energy storage devices from a scratch to a global industrial revolution,rechargeable batteries have become an imperative game-changer,but with the endless increase in the global per capita usage of energy,the appeal of high-performance,low-cost rechargeable batteries are being constantly increasing.Lithium-ion batteries(LIBs),being an essential class of reversible batteries,is a ruling candidate as a result of their impeccable energy density,enhanced cycle stability,increased voltage,reduced self-discharge,and extensive application from transportable devices to electrical vehicles.Although,the graphite,commercially recognized as an anode material of LIBs,is only contributing about 372 mA h g-1 of theoretical capacity by limiting LIBs overall performance.It is,therefore,need for an hour to develop some advanced electrode materials,which not only provide the energy contents but also do so at economical fronts.Lately,a vast amount of research efforts is being targeted on finding alternatives to conventional anode material(graphite)of LIB.Several anode materials have been studied up till now,but the transition metal oxides(TMO's)for instance Fe3O4,NiO,Co3O4,SnO2,and MnO2 as an anode material gained a lot of attention due to their three-fold theoretical capacity than that of graphite,low cost,and ample usefulness.By considering all the(TMO's),manganese dioxide(MnO2)has become a promising candidate due to their variety of polymorphic arrangements(?-,?-,?-,?-and ?-types,etc.),inexpensiveness,high voltage,environmental friendliness,non-toxicity,naturally abundant and high theoretical capacity(1232 mA h g-1).However,MnO2 also faces some limitations,for instance bulk MnO2 experienced an agglomeration,pulverization and volume expansion.Employing nano structuring technology to the MnO2 could be an effective solution to these issues because they provide large number of active sites and also support in narrowing down the diffusion path of electrons and Li ions.Nano structuring also does not eradicate all the problems of MnO2 such as volume expansion and aggregation during long time cycles.Many strategies were employed in order to solve this issue and with one of them is combining MnO2 with carbonaceous materials.Nowadays,graphene has become more provoking than any other carbonaceous materials due to its enhanced electrical conductivity and containment of carbon atoms in honeycomb monolayer assembly with the adoption of sp2 bonding configuration.Graphene oxide(GO)being a part of graphene equipped with oxygen functionalities therefore has an ability to associate MnO2 with itself by the help of these functionalities.This design will inhibit the aggregation of MnO2 nanostructure;above all,GO will reduce the volume expansion during the charge-discharge operation.Herein,a highly efficient hybrid material of MnO2 nanotubes and GO(GMN)is being presented as an anode material for the application of LIBs,manufactured by a simple and cost-effective approaches(sonication and hydrothermal reaction).By employing a sonication approach a composite of MnO2 and 'as is' GO(GMN)was fabricated by the assistance of Mn-O-C bridges.We report GO,which has vast potential to be utilize 'as is' electrode material in LIB with metal oxide,rather than to be used it as a precursor to obtained reduced graphene oxide and then take benefits,which is a case for most of the reported work previously.Consequently,obtained GMN composite presents enormous gravimetric capacity of 1290 mA h g-1 at 0.1 A g-1,68 percent initial columbic efficiency and nearly three times lower volume expansion in contrast to bare MnO2.The other technique that was employed to fabricate a composite named as HGMN was hydrothermal approach.This technique transforms the MnO2 nanotubes into MnO2 nanoparticles via hydrothermal method by utilizing GO as a morphology-control agent for controlled fabrication of MnO2 nano crystals.The slicing of MnO2 nanotubes into smaller nano particles will become a source of abundant interspaces giving considerable amount of electrochemical active sites and also unhindered channels for the operation of lithiation and delithiation.Consequently,attained HGMN composite possesses a tremendous gravimetric capacity of 1048 mA h g-1,enhanced initial columbic efficiency of 71%,increased rate property and reduced charge transfer resistance.