Dual-Modified Electrospun Fiber Membrane as Separator with Excellent Safety Performance and High Operating Temperature for Lithium-Ion Batteries.

Polyacrylonitrile/Boric acid/Melamine/the delaminated BN nanosheets electrospun fiber membrane (PB3N1BN) with excellent mechanical property, high thermal stability, superior flame-retardant performance, and good wettability are fabricated by electrospinning PAN/DMF/H3BO3/C3H6N6/ the delaminated BN nanosheets (BNNSs) homogeneous viscous suspension and followed by a heating treatment. BNNSs are obtained by delaminating the bulk h-BN in isopropyl alcohol (IPA) with an assistance of Polyvinylpyrrolidone (PVP). Benefiting from the cross-linked pore structure and high-temperature stability of BNNSs, PB3N1BN electrospun fiber membrane delivers high thermal dimensional stability (almost no size contraction at 200 °C), excellent mechanical property (19.1 MPa), good electrolyte wettability (contact angle about 0°), and excellent flame retardancy (minimum total heat release of 3.2 MJ m-2). Moreover, the assembled LiFePO4/PB3N1BN/Li asymmetrical battery using LiFePO4 as the cathode and Li as the anode has a high capacity (169 mAh g-1 at 0.5 C), exceptional rate capability (129 mAh g-1 at 5 C), the prominent cycling stability without obvious decay after 400 cycles, and a good discharge capacity of 152 mAh g-1 at a high temperature of 80 °C. This work offers a new structural design strategy toward separators with excellent mechanical performance, good wettability, and high thermal stability for lithium-ion batteries.

CoNi2 S4 Nanoparticle/Carbon Nanotube Sponge Cathode with Ultrahigh Capacitance for Highly Compressible Asymmetric Supercapacitor.

Compared with other flexible energy-storage devices, the design and construction of the compressible energy-storage devices face more difficulty because they must accommodate large strain and shape deformations. In the present work, CoNi2 S4 nanoparticles/3D porous carbon nanotube (CNT) sponge cathode with highly compressible property and excellent capacitance is prepared by electrodepositing CoNi2 S4 on CNT sponge, in which CoNi2 S4 nanoparticles with size among 10-15 nm are uniformly anchored on CNT, causing the cathode to show a high compression property and gives high specific capacitance of 1530 F g-1 . Meanwhile, Fe2 O3 /CNT sponge anode with specific capacitance of 460 F g-1 in a prolonged voltage window is also prepared by electrodepositing Fe2 O3 nanosheets on CNT sponge. An asymmetric supercapacitor (CoNi2 S4 /CNT//Fe2 O3 /CNT) is assembled by using CoNi2 S4 /CNT sponge as positive electrode and Fe2 O3 /CNT sponge as negative electrode in 2 m KOH solution. It exhibits excellent energy density of up to 50 Wh kg-1 at a power density of 847 W kg-1 and excellent cycling stability at high compression. Even at a strain of 85%, about 75% of the initial capacitance is retained after 10 000 consecutive cycles. The CoNi2 S4 /CNT//Fe2 O3 /CNT device is a promising candidate for flexible energy devices due to its excellent compressibility and high energy density.

Preparation and formation process of α-MnS@MoS2 microcubes with hierarchical core/shell structure.

α-MnS@MoS2 microcubes with hierarchical core/shell structure are prepared by one-step hydrothermal method in a reaction system of δ-MnO2 nanowires, thioacetamide and Na2MoO4 at 200°C for 24h, and the formation process and phase transition behavior has been investigated in detail. Research results indicate that uniform nanosheets of MoS2 with thickness of about 20nm and size up to hundreds of nanometers are vertically grow on the surface of α-MnS core, and the amount of sodium molybdate plays a crucial role in adjusting the crystal phase and structure of the obtained materials. The formation process of α-MnS@MoS2 microcubes with hierarchical core/shell structure consist of four stages, δ-MnO2 nanowires with layered structure are firstly transforms into tetragonal Mn3O4 nanoparticles, then into γ-MnS hexagonal prisms and α-MnS microcubes, and finally into α-MnS@MoS2 microcubes. In compare with ß-MnS and γ-MnS phases, α-MnS can be formed in α-MnS@MoS2 microcubes because it has not only higher lattice energy, but also the lowest Gibbs free energy and the sufficient activation energy at high hydrothermal treatment temperature. By using this one-step hydrothermal technology without template assisted route, other transition metal sulfide materials with novel core/shell structure and morphology can be designed and prepared by selecting transition metal and adjusting the amount of sulfur source.