One-pot In-situ Synthesis of Sn/Carbon-fibers Nanocomposite by Chemical Vapor Deposition and Its Li-storage Properties

Sn/carbon-fibers（CFs） nanocomposite has been prepared by chemical vapor deposition with in-situ catalytic growth of CFs.The nanocomposite has been characterized by X-ray diffraction（XRD）,field emission scanning electron microscopy（FE-SEM）,transmission electron microscopy（TEM） and Raman spectrum.The electrochemical performance of the nanocomposite has been investigated by galvanostatic cycling and cyclic voltammetry（CV）.It has been found that a three-dimensional conductive network forms by the interconnected CFs,which offers conductive channels for the Sn nanoparticles.The nanocomposite gives a first charge capacity of 385 mAh.g-1 and exhibits an improved cycling stability than bare Sn.

Enhanced Ionic Accessibility of Flexible MXene Electrodes Produced by Natural Sedimentation

MXene nanosheets have been used for preparing highly flexible integrated electrodes due to their two-dimensional(2D)morphology,flexibility,high conductivity,and abundant functional groups.However,restacking of 2D nanosheets inhibits the ion transport in MXene electrodes,limiting their thickness,rate performance,and energy storage capacity.Here,we employed a natural sedimentation method instead of the conventional vacuum-assisted filtration to prepare flexible Ti3C2TxMXene films with enlarged interlayer spacing,which facilitates the access of the lithium ions to the interlayers and thus leads to a greatly enhanced electrochemical performance.The naturally sedimented flexible film shows a double lithium storage capacity compared to the conventional vacuum-filtered MXene film,along with improved rate performance and excellent cycle stability.

Recent Progress and Design Principles for Rechargeable Lithium Organic Batteries

The most commonly used electrode materials in lithium organic batteries(LOBs)are redox-active organic materials,which have the advantages of low cost,environmental safety,and adjustable structures.Although the use of organic materials as electrodes in LOBs has been reported,these materials have not attained the same recognition as inorganic electrode materials,mainly due to their slight electronic conductivity and possible solubility in organic electrolytes,resulting in a low reversible capacity.However,over the past 10 years,organic materials have achieved outstanding results when used as battery electrodes,and an increasing number of researchers have realized their significance.This review summarizes the recent progress in organic electrodes for use in rechargeable LOBs.By classifying Li-storage mechanisms with various functional organic groups and designing molecules for next-generation advanced lithium organic systems,we attempt to analyze the working principle and the effect of various organic functionalities on electrochemical performance,to reveal the advantages and disadvantages of various organic molecules and to propose possible design principles and development trends for future LOBs.In addition,we highlight the recently reported two-dimensional covalent organic framework that is unique in its extensiveπconjugated structure and Li-storage mechanisms based on benzene and N-containing rings;this framework is considered to be the most promising alternative to metal-based electrode materials with comparable large reversible capacities and long cycle lives.

Anisotropic black phosphorene nanotube anodes afford ultrafast kinetic rate or extra capacities for Li-ion batteries

As an important anode material for fast-charging Li-ion batteries(LIBs),black phosphorus(BP)has attracted extensive attention.Black phosphorene nanotubes(BPNTs)can be theoretically produced by rolling up the black phosphorene nanosheet along armchair(a-BPNTs)and zigzag(z-BPNTs)directions.The effects of curvature,chirality,Li-storage concentrations and strain stress on the Li-storage performance such as Li diffusion barriers and mechanical stabilities of BPNTs are mainly investigated by first principles calculations.The theoretical calculations predict that the a-BPNTs and z-BPNTs have good maximum Li-storage capacities,and the z-BPNTs exhibit better flexibility than a-BPNTs.The mechanical stabilities and Li-migration are all related to the curvature of BPNTs.Additionally,both a-BPNTs and z-BPNTs exhibit fast Li-ion conductivity along the c-axis direction.Moreover,the average Poisson's ratio of a-BPNTs(0.68)is larger than that of z-BPNTs(0.17),indicating that the strain stress is more difficult to apply on a-BPNTs than z-BPNTs.Our calculations predict that the a-BPNTs can afford ultrafast kinetic rate for fastcharging and high-power LIBs,while the z-BPNTs can provide extra capacity for high-energy LIBs.

Li-ion storage performance and electrochemically induced phase evolution of layer-structured Li[Li0.2Mn0.54Ni0.13Co0.13]02 cathode material

Li-rich Li[Li0.2Mn0.54Ni0.13Co0.13]02（LMNC） powders were synthesized by a gel-combustion method. The related microstructure, electrochemical performance and electrochemically induced phase evolution were characterized. The 900℃ calcined powders have a hexagonal layered structure with high ordered degree and low cationic mixing level. The calcined materials as cathode electrode for Li-ion battery deliver the high electrochemical properties with an initial discharge capacity of 243.5 mA. h. g-1 at 25 mA.g-1 and 249.2 mA-h.g-1 even after 50 cycles. The electrochemically induced phase evolution investigated by a transmission electron microscopy indicates that Li＋ ions deintercalated first from the LiMO2 （M = Mn, Co, Ni） component and then from Li2MnO3 component in the LMNC during the charge process, while Li＋ ions intercalated into Li1-xMO2 component followed by into MnO2 component during the discharge process.