Solution Synthesis of Iodine-Doped Red Phosphorus Nanoparticles for Lithium-Ion Battery Anodes

Red phosphorus (RP) is a promising anode material for lithium-ion batteries due to its earth abundance and a high theoretical capacity of 2596 mA h g^–1. Although RP-based anodes for lithium-ion batteries have been reported, they were all in the form of carbon–P composites, including P–graphene, P–graphite, P–carbon nanotubes (CNTs), and P–carbon black, to improve P’s extremely low conductivity and large volume change during cycling process. Here, we report the large-scale synthesis of red phosphorus nanoparticles (RPNPs) with sizes ranging from 100 to 200 nm by reacting PI₃ with ethylene glycol in the presence of cetyltrimethylammonium bromide (CTAB) in ambient environment. Unlike the insulator behavior of commercial RP (conductivity of <10 ^–12 S m^–1), the conductivity of RPNPs is between 2.62 × 10^–3 and 1.81 × 10^–2 S m^–1, which is close to that of semiconductor germanium (1.02 × 10^–2 S m^–1), and 2 orders of magnitude higher than silicon (5.35 × 10^–4 S m^–1). Around 3–5 wt % of iodine-doping was found in RPNPs, which was speculated as the key to significantly improve the conductivity of RPNPs. The significantly improved conductivity of RPNPs and their uniform colloidal nanostructures enable them to be used solely as active materials for LIBs anodes. The RPNPs electrodes exhibit a high specific capacity of 1700 mA h g^–1 (0.2 C after 100 cycles, 1 C = 2000 mA g^–1), long cycling life (∼900 mA h g^–1 after 500 cycles at 1 C), and outstanding rate capability (175 mA h g^–1 at the charge current density of 120 A g^–1, 60 C). Moreover, as a proof-of-concept example, pouch-type full cells using RPNPs anodes and Li­(Ni_0.5Co_0.3Mn_0.2)­O₂ (NCM-532) cathodes were assembled to show their practical uses

Phosphorus-Rich Copper Phosphide Nanowires for Field-Effect Transistors and Lithium-Ion Batteries

Phosphorus-rich transition metal phosphide CuP₂ nanowires were synthesized with high quality and high yield (∼60%) via the supercritical fluid–liquid–solid (SFLS) growth at 410 °C and 10.2 MPa. The obtained CuP₂ nanowires have a high aspect ratio and exhibit a single crystal structure of monoclinic CuP₂ without any impurity phase. CuP₂ nanowires have progressive improvement for semiconductors and energy storages compared with bulk CuP₂. Being utilized for back-gate field effect transistor (FET) measurement, CuP₂ nanowires possess a p-type behavior intrinsically with an on/off ratio larger than 10⁴ and its single nanowire electrical transport property exhibits a hole mobility of 147 cm² V^–1 s^–1, representing the example of a CuP₂ transistor. In addition, CuP₂ nanowires can serve as an appealing anode material for a lithium-ion battery electrode. The discharge capacity remained at 945 mA h g^–1 after 100 cycles, showing a good capacity retention of 88% based on the first discharge capacity. Even at a high rate of 6 C, the electrode still exhibited an outstanding result with a capacity of ∼600 mA h g^–1. <i>Ex-situ</i> transmission electron microscopy and CV tests demonstrate that the stability of capacity retention and remarkable rate capability of the CuP₂ nanowires electrode are attributed to the role of the metal phosphide conversion-type lithium storage mechanism. Finally, CuP₂ nanowire anodes and LiFePO₄ cathodes were assembled into pouch-type lithium batteries offering a capacity over 60 mA h. The full cell shows high capacity and stable capacity retention and can be used as an energy supply to operate electronic devices such as mobile phones and mini 4WD cars

Phosphorus-Rich Copper Phosphide Nanowires for Field-Effect Transistors and Lithium-Ion Batteries

Phosphorus-rich transition metal phosphide CuP₂ nanowires were synthesized with high quality and high yield (∼60%) via the supercritical fluid–liquid–solid (SFLS) growth at 410 °C and 10.2 MPa. The obtained CuP₂ nanowires have a high aspect ratio and exhibit a single crystal structure of monoclinic CuP₂ without any impurity phase. CuP₂ nanowires have progressive improvement for semiconductors and energy storages compared with bulk CuP₂. Being utilized for back-gate field effect transistor (FET) measurement, CuP₂ nanowires possess a p-type behavior intrinsically with an on/off ratio larger than 10⁴ and its single nanowire electrical transport property exhibits a hole mobility of 147 cm² V^–1 s^–1, representing the example of a CuP₂ transistor. In addition, CuP₂ nanowires can serve as an appealing anode material for a lithium-ion battery electrode. The discharge capacity remained at 945 mA h g^–1 after 100 cycles, showing a good capacity retention of 88% based on the first discharge capacity. Even at a high rate of 6 C, the electrode still exhibited an outstanding result with a capacity of ∼600 mA h g^–1. <i>Ex-situ</i> transmission electron microscopy and CV tests demonstrate that the stability of capacity retention and remarkable rate capability of the CuP₂ nanowires electrode are attributed to the role of the metal phosphide conversion-type lithium storage mechanism. Finally, CuP₂ nanowire anodes and LiFePO₄ cathodes were assembled into pouch-type lithium batteries offering a capacity over 60 mA h. The full cell shows high capacity and stable capacity retention and can be used as an energy supply to operate electronic devices such as mobile phones and mini 4WD cars

Stereochemical Course of Wittig Rearrangements of Dihydropyran Allyl Propargyl Ethers

[2,3]-Wittig rearrangements of sugar-derived dihydropyran allyl propargyl ethers located at the 2- or 4-position have been studied as useful means for extending the carbon chains of the 4- or 2-position with chirality transfer. The stereochemical course of these reactions depends on the following factors: (1) deprotonation of <i>pro</i>-<i>R</i> or <i>pro</i>-<i>S</i>-H, (2) equilibration of the lithiated stereogenic carbanion, (3) conformational inversion during the rearrangement, and (4) concerted [2,3]- or [1,2]-Wittig rearrangement. In some cases, a stepwise mechanism that involves the allyl-C–O bond cleavage is shared as the first step by both the [2,3]- and [1,2]-Wittig rearrangements. The stereochemical courses of the rearrangements are compared among the lithiated reactants to determine the reaction pathways. These mechanisms in the polyoxygenated dihydropyran ring system were further supported by DFT calculations

Spray-Deposited Large-Area Copper Nanowire Transparent Conductive Electrodes and Their Uses for Touch Screen Applications

Large-area conducting transparent conducting electrodes (TCEs) were prepared by a fast, scalable, and low-cost spray deposition of copper nanowire (CuNW) dispersions. Thin, long, and pure copper nanowires were obtained via the seed-mediated growth in an organic solvent-based synthesis. The mean length and diameter of nanowires are, respectively, 37.7 μm and 46 nm, corresponding to a high-mean-aspect ratio of 790. These wires were spray-deposited onto a glass substrate to form a nanowire conducting network which function as a TCE. CuNW TCEs exhibit high-transparency and high-conductivity since their relatively long lengths are advantageous in lowering in the sheet resistance. For example, a 2 × 2 cm² transparent nanowire electrode exhibits transmittance of <i>T</i> = 90% with a sheet resistance as low as 52.7 Ω sq^–1. Large-area sizes (>50 cm²) of CuNW TCEs were also prepared by the spray coating method and assembled as resistive touch screens that can be integrated with a variety of devices, including LED lighting array, a computer, electric motors, and audio electronic devices, showing the capability to make diverse sizes and functionalities of CuNW TCEs by the reported method