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[[Vol. 37]Metal Oxide_Graphene Nanosheet Composite Exhibits Unprecedented Energy Storage Properties_ WPI-MANA.pdf](https://mdr.nims.go.jp/filesets/ccef21c2-1261-4887-9632-46ff9c4120b8/download)

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International Center for Materials Nanoarchitectonics (WPI-MANA)

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[[Research Highlights Vol.37] Metal Oxide/Graphene Nanosheet Composite Exhibits Unprecedented Energy Storage Properties](https://mdr.nims.go.jp/datasets/50232498-e115-4bb4-85a4-4b8cc1611fe3)

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2022/04/04 10:07 Metal Oxide/Graphene Nanosheet Composite Exhibits Unprecedented Energy Storage Properties| MANAhttps://www.nims.go.jp/mana/research/highlights/vol37.html 1/3Previous  Index  NextResearch Highlights[Vol. 37]Metal Oxide/Graphene Nanosheet Composite Exhibits Unprecedented EnergyStorage Properties29 Mar, 2018Single-layer metal oxide nanosheets sandwiched between graphene layers exhibitrecord energy storage figures of merit.Figure: Structure of MnO2/graphene superlattice-like structure and electrochemicalcharacteristics of Li and Na batteries fabricated using this material.The unique physical properties of nanomaterials are important for the realization of highperformance energy storage devices. For example, the ultra-narrow spaces between multilayeredtwo-dimensional (2D) nanosheets are suitable for high efficiency ion intercalation, namely,reversible insertion of ions into the spaces between layers. Importantly, nanomaterial structureswith nearly ideal nano interlayer spaces for ion intercalation exhibit short diffusion distances andlarge numbers of active sites —properties that are essential for fabricating electrode materials ofhigh performing energy storage devices.However, despite extensive research on 2D materials such as graphene and transition metaldichalcogenides the energy storage capacity has not met expectations. More recently, research hashttps://www.nims.go.jp/mana/research/highlights/vol36.htmlhttps://www.nims.go.jp/mana/research/highlights/index.htmlhttps://www.nims.go.jp/mana/research/highlights/vol38.html2022/04/04 10:07 Metal Oxide/Graphene Nanosheet Composite Exhibits Unprecedented Energy Storage Properties| MANAhttps://www.nims.go.jp/mana/research/highlights/vol37.html 2/3also turned to explore 2D metal oxides—materials with many more active sites, and even shorterdiffusion lengths. The main issues to resolve include synthesis of genuine single layered metaloxides, prevention of ‘restacking’ during chemical processes to fabricate electrodes, and improvingtheir electrical conductivity.Here, a group led by Takayoshi Sasaki at the International Center for Materials Nanoarchitectonics(WPI-MANA), National Institute for Materials Science (NIMS), Tsukuba, Japan, describe thesynthesis of superlattice-like MnO2/graphene 2D nanostructures that exhibited the best figures ofmerit for energy storage reported to-date.The researchers synthesized the MnO2/graphene superlattice structures by ‘electrostatic assembly’of MnO2 and graphene in a solution, exploiting the differences in the charged states of therespective materials: The MnO2 nanosheets are negatively charged and reduced graphene oxide(rGO) nanosheets are positive. The two important points about this fabrication process and theresulting nanosheet structures are that the MnO2 nanosheets were ‘genuine unilamellar’ structuresand each of the MnO2 nanosheets was ‘stabilized’ between the atomic layers of graphene.The MnO2/graphene nanostructures were used as anodes for Li and Na ion batteries.Electrochemical measurements showed specific capacities of 1325 and 795 mA h g−1 at 0.1 Ag−1 and 370 and 245 mA h g−1 at 12.8 A g−1 for Li and Na storage, respectively. “Moreimportantly, an ultralong cyclability with 0.004% and 0.0078% capacity decay per cycle up to 5000cycles was achieved for Li and Na storage, respectively, outperforming previously reported metaloxide-based anodes to date,” state the authors.“The superlattice composite material described in this paper is based on MANA’s concept of‘Materials Nanoarchitectonics’, says Sasaki. “We have taken two types of 2D materials with differingproperties and formed an advanced composite material with synergistic characteristics that are notexhibited by a single material.”Reference“Genuine Unilamellar Metal Oxide Nanosheets Confined in a Superlattice-like Structure for SuperiorEnergy Storage”Pan Xiong, Renzhi Ma, Nobuyuki Sakai, and Takayoshi SasakiJournal : ACS Nano, 12 ,1768–1777, (2018).DOI : 10.1021/acsnano.7b08522AffiliationsInternational Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for MaterialsScience (NIMS), Namiki 1-1, Tsukuba, Ibaraki 305-0044, JapanContact informationInternational Center for Materials Nanoarchitectonics(WPI-MANA)https://samurai.nims.go.jp/profiles/ma_renzhi?locale=enhttps://samurai.nims.go.jp/profiles/sakai_nobuyuki?locale=enhttps://samurai.nims.go.jp/profiles/sasaki_takayoshi?locale=enhttps://pubs.acs.org/doi/10.1021/acsnano.7b085222022/04/04 10:07 Metal Oxide/Graphene Nanosheet Composite Exhibits Unprecedented Energy Storage Properties| MANAhttps://www.nims.go.jp/mana/research/highlights/vol37.html 3/3National Institute for Materials Science1-1 Namiki, Tsukuba, Ibaraki 305-0044 JapanPhone: +81-29-860-4710E-mail: mana-pr[AT]ml.nims.go.jp