Li has been considered as the ultimate anode material for high energy density secondary Li batteries. However, its practical application has been limited due to its low Coulombic efficiency (CE) and the formation of lithium dendrites. Recently, we have developed a microspherical Li-carbon nanotube (Li-CNT) composite material passivated with octadecylphosphonic acid (OPA) self-assembled monolayer (SAM) exhibiting suppressed lithium dendrite formation and improved environmental/electrochemical stability. In this work, we demonstrated the significantly enhanced passivation effects of a SAM using dihexadecanoalkyl phosphate (DHP), a molecule that is comprised of double hydrophobic alkyl chains and forms a denser SAM on surfaces with large curvature. As a result, the DHP SAM delivers superior environmental and electrochemical stability to the OPA passivated Li-CNT material. In specific, the DHP passivated Li-CNT composite (DHP-Li-CNT) delivers a high CE of 99.25% under a 33.3% depth of discharge (DOD) at 1 C, when it is paired with a LiFePO₄ cathode. The evolution of the SAM during cycling and the effects of DOD and current density on the CE of the DHP-Li-CNT anode have also been investigated. The improved SAM passivation constitutes an important step in achieving the goal of practically applicable Li anodes.

Organic-based electrode materials for lithium-ion batteries (LIBs) are promising due to their high theoretical capacity, structure versatility and environmental benignity. However, the poor intrinsic electric conductivity of most polymers results in slow reaction kinetics and hinders their application as electrode materials for LIBs. A binder-free self-supporting organic electrode with excellent redox kinetics is herein demonstrated via in situ polymerization of a uniform thin polyimide (PI) layer on a porous and highly conductive carbonized nanofiber (CNF) framework. The PI active material in the porous PI@CNF film has large physical contact area with both the CNF and the electrolyte thus obtains superior electronic and ionic conduction. As a result, the PI@CNF cathode exhibits a discharge capacity of 170 mAh·g^-1 at 1 C (175 mA·g^-1), remarkable rate-performance (70.5% of 0.5 C capacity can be obtained at a 100 C discharge rate), and superior cycling stability with 81.3% capacity retention after 1, 000 cycles at 1 C. Last but not least, a four-electron transfer redox process of the PI polymer was realized for the first time thanks to the excellent redox kinetics of the PI@CNF electrode, showing a discharge capacity exceeding 300 mAh·g^-1 at a current of 175 mA·g^-1.

The power conversion efficiency of organometallic perovskite-based solar cells has skyrocketed in recent years. Intensive efforts have been made to prepare high-quality perovskite films tailored to various device configurations. Planar heterojunction devices have achieved record efficiencies; however, the preparation of perovskite films for planar junction devices requires the use of expensive vacuum facilities and/or the fine control of experimental conditions. Here, we demonstrate a facile preparation of perovskite films using solid-state chemistry. Solid-state precursor thin films of CH₃NH₃I and PbI₂ are brought into contact with each other and allowed to react via thermally accelerated diffusion. The resulting perovskite film displays good optical absorption and a smooth morphology. Solar cells based on these films show an average efficiency of 8.7% and a maximum efficiency of 10%. The solid-state synthesis of organometallic perovskite can also be carried out on flexible plastic substrates. Using this method on a PET/ITO substrate produces devices with an efficiency of 3.2%. Unlike existing synthetic methods for organometallic perovskite films, the solid-state reaction method does not require the use of orthogonal solvents or careful adjustment of reaction conditions, and thus shows good potential for mass production in the future.

Intrinsic carrier transport properties of single-walled carbon nanotubes have been probed by two parallel methods on the same individual tubes: The contactless dielectric force microscopy (DFM) technique and the conventional field-effect transistor (FET) method. The dielectric responses of SWNTs are strongly correlated with electronic transport of the corresponding FETs. The DC bias voltage in DFM plays a role analogous to the gate voltage in FET. A microscopic model based on the general continuity equation and numerical simulation is built to reveal the link between intrinsic properties such as carrier concentration and mobility and the macroscopic observable, i.e. dielectric responses, in DFM experiments. Local transport barriers in nanotubes, which influence the device transport behaviors, are also detected with nanometer scale resolution.