Research On Energy Storage Devices Based On Carbon Nanomaterials And Nanostructured Manganese Oxides

Due to the high energy,high safety,high thermodynamic stability,low potential and low cost,nanostructured manganese oxides have not only attracted much attention in traditional electrochemical energy storage(EES)devices such as lithium ion batterie(LIB),but also become a research hotspot in some new EES devices such as lithium ion capacitor(LIC)and zinc ion battery(ZIB).However,the inherent drawbacks including poor conductivity,large volume variation as well as poor structure and interface stability have limited the further development.Graphene and carbon nanotubes not only can become the key to solve the above problems of manganese oxides,but also can broaden and enhance their application in EES devices.In this paper,high-performance EES devices based on carbon nanomaterials and nanostructured manganese oxides were constructed through rational design for both material structure and device configuration.The research works are as follows:1.To solve the problems of poor reaction kinetics as well as the interface and structure stability of Mn O,an anode for lithium ion battery was constructed based on 10-nanometer ultrafine Mn O nanowires(NWs)and graphene.Through the systematic study of the relationship between structure and performance,we found that 2D graphene was scrolled along Mn O NWs to form a 1D core-shell structure.This core-shell structure can not only improve the electron transport capacity,but also restrain the volume change of Mn O NWs to improve the structure and interface stability.Meanwhile,the 1D core-shell structure was embedded in the 2D graphene sheets and self-assembled to form 3D graphene aerogel monolith,which guarantee the electron transfer and ion diffusion throughout the whole electrode.In addition,the formation mechanism of the composite electrode was analyzed,and the influence of the radial dimension of Mn O NWs on the reaction kinetics especially the ion diffusion kinetics was also investigated.Further,the self-supported electrodes with high density and high areal loads were prepared,and a holey treatment on the graphene via H₂O₂ etching was conducted to improve the sluggish ion transport in such a thick electrode with high areal loads.2.To further promote the reaction kinetics of Mn O anode to meet the requirements of LICs,a self-supported architecture was designed by combining an interconnected graphene scroll(GS)framework with in situ formed well-distributed Mn O nanoparticles(NPs)(?45 nm).In this architecture,the inner-connected tubular GS framework plays a multifunctional role:serving as an electron transport bridge like“highways”,providing a favorable ion transport pathway as well as accommodating the volume expansion and maintaining the structural stability of Mn O.Benefiting from the stable structure,highly localized charge-transfer and low energy diffusion barrier,the as-built anode exhibits an ultrahigh-rate behavior and robust cycling stability.When evaluated as a self-supported anode for LIC,the LIC delivers a high energy density of 179.3 Wh kg^-1,a high power density of 11.7 k W kg^-1,and a capacity retention of 80.8%after 5000 cycles.3.To develop the energy storage devices with high security,the aqueous ZIB has been constructed.However,the ZIB used to have poor cycle life due to the dendrite growth of Zn anode.A dendrite-free and stable CNT film/Zn anode has been prepared by using a continuous CNT film as the protective layer.The CNT film is composed of 3D interconnected CNTs with"Y"nodes,which have excellent electrical conductivity.Thus,the charge distribution on the Zn anode can be uniform and the local charge accumulation can be avoided.The results showed that the CNT film/Zn anode had a lower deposition/stripping overpotential(?50 m V)and more stable deposition/stripping time(more than 1000 hours).Besides,a Zn//Mn O₂ ZIB based on this CNT film/Zn anode showed significantly improved cycle stability.4.An integrated battery configuration for aqueous ZIB bas been further developed to realize the high flexibility and long life.In this integrated configuration,the Zn anode was coated with a protective coating consisting of zinc trifluoromethylsulfonate and polyamide(PA).This protective coating can not only inhibit the dendrite growth and side reactions,but also act as a glue to bind the Zn anode with PA separator tightly.A highly flexible cathode with conductive network was constructed by cross-linking MWCNTs and Mn O₂ NWs.Then this cathode was loaded on the other side of the PA separator and played a dual role:not only act as the cathode to accommodate Zn²⁺,but also as the collector.Benefit from the continuous and seamless connection between components in the ultimate integrated configuration,relative displacement or separation between adjacent components can be prevented under different mechanical deformations,guaranteeing stable active load and/or electronic transmission.The results demonstrated that the integrated ZIB not only had a good flexibility(the capacity retention rate>90%after 1000 bends),but also had a significantly improved cycling stability compared with the traditional segregated electrode structure(the capacity retention after 5000 cycles was 89.4%).