Synthesis Of Novel Biomass-based Energy Storage And Electromagnetic Shielding Materials By Magnetron Sputtering

Agroforestry biomass is an inexhaustible resource on earth and can serve as raw material to prepare large surface area and high reaction activity of novel products(e.g.,1D nanofibrils,2D nanofilms and 3D gels)through disassembly and reassembly.These novel biomass-derived products can act as substrates to integrate with micro-nano functional units for the development of green and new biomass-based functional composites.These substrates not only endow the composites with many merits(like environmental friendliness,flexibility and hydrophilicity),but also can be used as microchambers to induce the deposition of micro-nano functional units and inhibit their agglomeration.Previous researches have demonstrated that,in the preparation of biomass-based functional composites,the purity,size and micromorphology of micro-nano functional units and the interface bonding effects between the units and the substrates play key roles in the core property of composites.As a result it is of great significance to develop new preparation strategies to achieve the precise control of the purity,size and micromorphology of micro-nano units and promote the efficient interface integration between multiple components.Based on these issues,in this paper,we introduced and combined the high-precision magnetron sputtering technology with postprocessing methods(like cyclic voltammetry electrooxidation),to grow micro-nano active materials with precisely controllable microstructure and size on the surface of various biomass-derived substrates(such as cellulose fibers,cellulose paper and cellulose-derived porous carbon).These processes lead to the generation of high-performance electrochemical energy storage materials and electromagnetic shielding materials,expanding the high-value utilization ways of biomass resource.The main content and results of the present paper can be summarized as follows:(1)A facile combined method of magnetron sputtering and electrooxidation was used to imitate a natural geologic architecture system(i.e.,"ground-mountain-vegetation"),leading to the formation of a ternary compound system(namely cellulose fibers-supported Co@Co(OH)2 heterostructure)whose structure and function are similar to those of the natural system.Thanks to the synergistic effects of this ternary structure(i.e.,the storage capacity of cellulose substrate("ground")for electrolyte ions,electron superhighway supplied by interlayered metallic Co("mountain"),and ultra-high electrochemical activity and mechanical stability of in-situ grown and quasi-honeycomb Co(OH)2("vegetation")with large surface area),the supercapacitor device assembled by the nature-inspired materials exhibits highly competitive energy density(166 μWh cm-2).Also,after 10000 cycles at a high current density,the capacitance loss ratio is only 8.4%.The mechanism analysis demonstrates that both Co(OH)2 and CoOOH have the same layered cobalt structure,sparing massive structural changes for this phase transformation,which contributes to high long cycling life.(2)Two facile and fast steps(including magnetron sputtering and electro-oxidation)were developed to grow forest-like Cu2O/Cu array onto the 3D flexible cellulose fiber framework.The ternary composite can serve as a flexible and free-standing electrode,which shows a high specific capacitance of 915 F g-1 and superior cycling stability as well as high rate performance.The synergistic effects of multiple components and the abundant electrochemical reaction sites provided by the forest-like multiscale array play crucial roles in the excellent electrochemical properties.By growing the forest-like Cu2O/Cu array onto the two surfaces of cellulose paper,we can obtain a symmetrical supercapacitor device.The device has a high specific capacitance of 409 F g-1,superior specific energy of 24.0 W h kg-1 and excellent cycling stability(90.2%capacitance retention after 10000 cycles).(3)A combined method of magnetron sputtering and calcination was developed to prepare V2O5 nanoplates with a laminated structure.The V2O5 nanoplates were subsequently combined with cellulose-derived mesoporous carbon network via a ball-milling method.The mesoporous carbon network-encapsulated V2O5 nanoplates can serve as a novel cathode material,which delivers a high areal capacitance of 786 mF cm-2 at 0.2 mA cm-2 and superior cycle stability with an 89.5%capacitance retention after 5000 cycles.Besides,the electrode achieves an ultra-high rate capability(82%capacitance retention as the current density increases by 25 times from 0.2 mA cm-2 to 5 mA cm-2).In addition,an asymmetric supercapacitor assembled using this cathode and the mesoporous carbon network anode has superior electrochemical properties,e.g.,high operating voltage,long cycle life and large energy density(72.2 μWh cm-2 at the power density of 0.16 W cm-2).(4)Cotton fiber fabrics were employed as feedstock to prepare electrically conductive and hydrophobic carbon fibers.Then,nano-Cu was deposited onto the surface of carbon fibers via magnetron sputtering,leading to the formation of core-shell nano-Cu/carbon fibers composites.Th.e composite has superior hydrophobicity(water contact angle=144°)and high antibacterial activity against Escherichia coli and Staphylococcus aureus(antibacterial ratios:92.35%and 100%).In addition,on the basis of the nano-size effect and the synergistic effect between the two components,the nano-Cu/carbon fibers composites have high electromagnetic shielding property with a SEtotal value of 29.3 dB.To study the influence of thickness,the SSE and SSEt values were calculated to be 92 cm3 g-1 and 4621 dB cm2 g-1.Besides,the composites have an absorption-dominant electromagnetic interference shielding mechanism.(5)Based on the multi-dimensional and level-by-level assembly strategy,a high-precision combination technology of magnetron sputtering-plasma enhanced chemical vapor deposition was used to construct free-standing and sandwich-type nanoheterostructures,which consist of carbon fibers as the flexible substrate interlayer,metallic nickel nanoparticles as the conductive and magnetic middle layer,and dandelion-like graphene as highly conductive external layer.The bottom-up design can improve electromagnetic shielding performance with the help of the micro-nano structure and the synergistic effect between the multicomponents.The composites achieve an outstanding electromagnetic shielding effectiveness of～50.6 dB in the X-band(8.2-12.4 GHz)which can be classified as attenuation levels of "AAAA" for professional use.The high electrical conductivity,large heterogeneous interface area,residual defects/groups in graphene,homogeneous dispersion and magnetic responsiveness of Ni are directly associated with the excellent electromagnetic shielding property.