Structural Design And Properties Modification Of Two-dimensional Materials Based Flexible Energy Devices

Flexible energy storage devices such as supercapacitors and batteries,with high power/energy densities,are expected to play essential roles in our daily life as the dominant power sources for portable consumer electronics?e.g.,smartphones,tablets,notebook PCs and camcorders?.Flexible and wearable energy conversion and storage devices require flexible,lightweight,conductive materials with a large specific surface area to allow storing and releasing of“particles”?such as lithium ions,hydrogen atoms or molecules,or electric charges?.Graphene and the related two-dimensional?2D?crystals and their hybrid systems show several key properties that can address emerging energy needs,in particular for the ever growing market of portable and wearable energy conversion and storage devices.Graphene's flexibility,large surface area,and chemical stability,and its excellent electrical/thermal conductivities,promoting it applied in flexible electronic display and sensing fields.Chemically functionalized graphene can also improve storage and diffusion of ions and electric charge in batteries and supercapacitors.The other new two-dimentional?2D?crystals provide optoelectronic and photocatalytic properties complementing those of graphene,enabling the realization of ultrathin-film photovoltaic devices or systems for flexible energy conversion cell.In this paper,a series of two-dimentional based nanohybrids and macroscropic materials were designed and prepared.They show good performance in a wide range of applications especially in flexible energy conversion and strorage devices.Inspired by the calligraphy,we are delight to discover and presented a systematic study,which could shed light on GO ink transfer,macroscopic graphene film fabrication and other flexible electronics fabrication.It realizes large-scale preparation on rough,folded or even folded substrates,and obtains macro-reduced graphene oxide films with controllable size,thickness,shape and pore structure compare with the present methods?blade-coating,vacuum fitration,self-assembly et.al?.The films can be used as an electrode in supercapacitor and exhibite wide otential range?2.4 V?,high energy storage capacity(the areal capacitance is 258.6 mF?cm^-2,energy density of 23.1?Wh?cm^-2 at the power density of 0.2 mW?cm^-2).Furthermore,in order to improve the electrochemical energy storage ability,a new 2D material,molybdenum disulfide?MoS₂?was developed that with both pseudocapacitance and double-layer capacitance performance.Large area?>1?m?and ultra-thin?<20 nm?1T-MoS₂ nanosheets?NSs?were obtained by liquid chemical stripping technology as active materials.The nanosheet?MoS₂NSs?-encapsulated nanowires?AgNWs?were designed to achieve ultra-fast charge-discharge(50V?s^-1)and electrochemical stability?12.8%loss after 20,000 cycles?of the metal collector.With the help of spraying method,a large area of all-solid-state transparent mico-supercapacitor was obtained for the transparent elelctronic energy supply.As the wearble electronic developed,a hybrid 2D materials fiber and fibrous supercapacitor were produced for energy supply.By using wet-spinning method,reduced graphene oxide composite MoS₂?rGM?hybrid fiber was fabricated,and obtained an enhanced specific capacity(134.38 F·g^-1,332.85 mF·cm^-2 and 221.9 F·cm^-3 at the current density of 50 mA)were achieved.The MoS₂ modified rGO hybrid fibre also show high strength?109.44-204.27 MPa?and can be woven into textile directly.Three symmetrically assembled tandem and parallel ASFS groups formed textile have been fabricated and show tunable voltage output?1.0-2.6 V?,tailored capacitance,and outstanding flexible ability?100%of the initial capacitance when bent by 30°and60°?.For the flexible energy conversion application,2D materials are also needed to be self-standing,electroconductivity and conversion-applicable.Therefore,we further developed a strategy to build a 2D layerd materials-CNTs cross-linking structure based on 2D layerd networks.The obtained hybrid film exhibits good mechanical performance?54.72 MPa?,high-conductivity(10⁶ S?m^-1),low impedance and efficiently thermos-elelctrinic conversion behaviours owing to its unique three-dimentional?3D?structure based the 2D layerd materials cross-linking CNTs networks.A high performance all-solid-state supercapacitor was assembled based this film as electrode,which show6.9 mF?cm^-2 areal capaciyu,high rate(10 V?s^-1)and long-time?only 3.4%loss after 20,000 cycles?stability.The multi-functional elelctrode also can be used as a thermoelectric cell and haversing body heat,the output voltafe can reach 2.8 mV while the temperature difference is only 5 K.