Synthesis,characterization And Electrochemical Performance Of ?Ni,Co?MoO₄-Based Solid-Solution For Energy Storage Applications

Recently,significant efforts have been developed to fill the many future needs for electrochemical energy storage by employing new multi-functional materials.The exploration of efficient methodologies for the elaboration of oxide structures possessing multiple compositions appears as evidence for electrochemists and materials scientists given improving electrochemical performance.Indeed,the complex?binary and ternary?metal oxides?MOs?nanostructures are attracting a lot of attention thanks to their high electrochemical properties and their superior structure MOs for electrochemical energy storage?EES?systems such as lithium-ion batteries?LIBs?and hybrid supercapacitors?HSCs?,making them potential electrode materials.The research work introduced in this project is focused on the innovation,rational design and formation of novel nanostructured ternary metal molybdate oxides?TerMMOs?solid-solutions?SS?by converting the binary system into a ternary system to further enhance the electrochemical property,with porous texture for high-performance EES systems such as LIBs and HSCs.1.Electrochemical performances of HSCs and LIBs depend strongly on the micro-nanostructures of active materials as well as electrode configurations.Indeed,introducing one-dimensional?1D?nanostructures can effectively improve the cyclability of MO materials during cycles because 1D nanostructures can accommodate the strain of volume change caused by the lithiation/delithiation processes.Here,we develop through a facile two-step process the preparation of mesoporous Ni/Co-based molybdates oxide(Ni_x Co_1-x-x MoO₄)SS nanorods?NRs?with various stoichiometric molar ratios of Ni,and Co?Ni/Co:0.7:0.3,0.56:0.44,0.5:0.5,0.4:0.6,and 0.28:0.72?,by a modified hydrothermal method followed by a subsequent annealing process,and used as an electrode for HSCs and LIBs.The distinct micro-/nanostructures endow the Ni_0.5Co_0.5MoO₄ SSNRs sample with outstanding rate capacities at high current densities with enhanced capacity retention after 500 cycles as anode material for LIBs,and high specific capacitance as an electrode for HSCs compared to these counterpart.2.We present a facile fabrication of 1D Ni_0.5Co_0.5MoO₄.xH₂O?NCMO?SSNRs,NiMoO₄?NMO-NRs?,and CoMoO₄-xH₂O?CMO-NRs?,designed and synthesized using a two-step hydrothermal method.Considered as a high-performance material for HSCs and LIBs,the NCMO-SSNRs exhibits interesting electrochemical performances with high specific capacitance for the three-system electrode for HSCs,and good rate-performance as anode material for LIBs.Moreover,the hybrid NCMO-SSNRs//AC asymmetric device as-prepared displays an energy density?ED?of 45.45 Wh kg^-1 at a power density?PD?of 815 W kg^-1,and good cycle performance.The amazing capacitance retention after 9950 cycles was?93..These special performances of NCMO-SSNRs are attributable to its structural complexity,an alternative arrangement of nickel and cobalt species related to their same crystalline space group of Ni/Co-based molybdates,the approximate ionic radius between Ni²⁺?0.069 nm?and Co²⁺?0.074 nm?species as well as their near-identical electronegativity value located around1.88 and 1.91,significantly increases the diffusion of ions during electrochemical tests.3.We fabricated ultrafine 1D Ni_0.5Co_0.5MoO₄ SS nanoparticles?NPs?@ultra-long amorphous carbon nanofibers?ACNFs?through electrospinning technique.Indeed,NCMO-SS NPs have been dispersed uniformly in or on the surface of ACNFs.Noting that the ultra-small characters and the physicochemical properties would render further improve the electrical conductivity as well as serving as the cushion structure to alleviate the volume change during the charge-discharge process.The size distributions in these NPs had a mean diameter around?8.1 nm in the inner region of ACNFs,whereas the outer NPs at or near the surface of ACNFs were?19.2 nm.Moreover,this interesting material can effectively buffer the structural stress during Li-ions?Li⁺?insertion/extraction process,leading to highly reversible specific capacities at diverse densities.4.The rational design of dynamical TerMMOs with favorable microstructures and high-rate pseudocapacitance was explored using a bottom-up synthesis of hierarchical three-dimensional?3D?Ni_0.5Co_0.5MoO₄ SS nanosheet microsphere?NMS?self-constructed with mesoporous??2.6 nm?ultrathin nanosheet subunits of approximately 3.6-4.7 nm in thickness.The staggering developments in 3D hierarchical nanostructures,which offer a great opportunity to improve the performance of electrode for EES system.Otherwise,the NCMO-SSNMS provide a fast electron and ion transport,and large electroactive surface.More promisingly,our NCMO-SSNMS sample is largely highlighted as a competitive electrode for long-cycle-life hybrid supercapacitors,with good cycling stability.In brief,this research attempted to construct new TerMMOs SS micro/nanostructures,with various porous textures as electrodes for high performance electrochemical HSCs and LIBs.These different approaches reveal a significant improvement in the performance of EES,which has been directly linked to specific morphologies,compositions and porous textures of the electrode materials.Therefore,rational design of novel and unique nanomaterials with high electroconductivity and specific surfaces is fundamental for the development of high-performance HSCs and LIBs.