Xin Xia

A simple method to encapsulate SnSb nanoparticles into hollow carbon nanofibers with superior lithium-ion storage capability

The practical use of high-capacity anodes in lithium-ion batteries generally suffers from significant volume changes upon lithium insertion and extraction. The volume changes induce cracks and loss of inter-particle electronic contact in the electrode, resulting in rapid capacity decay. The use of fiber-like materials to prevent cracks and accommodate volume changes is widely observed in many animal and human activities. Birds mix grass and feathers into mud to build nests, and humans in ancient times blended straw with mud to produce adobe bricks for housing construction. In view of this point, this research designed a porous nanofiber structure to resolve the unstable structure problem of anode materials. The three-dimensional network structure composed of nanofibers provides a highly elastic matrix to accommodate the volume changes of high-capacity Sn and Sb particles and pores around the active particles, induced by CO2 evolution, serve as an additional buffer zone for the volume changes. This unique structure prepared by using a new SnSb alloy precursor and a simple electrospinning technique leads to excellent lithium storage performance in terms of energy density, cycling stability, and rate capability.

Investigations of lithium manganese oxide materials for lithium-ion batteries

Abstract As candidates for cathode materials in lithium-ion batteries, lithium manganese oxides are attractive and competitive. In this work, the feasibility of using a novel manganese oxide with a large-tunnel structure (i.e. todorokite, tunnel size: 3 × 3) as cathode material in lithiumion batteries has been explored. It is found that the initial capacity of todorokite material with Mg2+ in the tunnel is 151 mAh g−1 at a discharge current density of 0.1 mA cm−2. It still has a capacity of 128 mAh g−1 after four charge-discharge cycles. The effects of different cations, such as Co2+, Ni2+, Li+ etc., in the todorokite tunnel structure, on the electrochemical characteristics of the materials are also studied using slow-rate cyclic voltammetry and electrochemical impedance spectroscopy (EIS). Finally, the intercalation process of Li+ in the spinel manganese oxide films has been investigated using the in situ electrochemical quartz crystal microbalance (EQCM) method. It is shown that the intercalation process of Li+ in the films can be divided into at least two stages. The results also implied co-intercalation of solvent with Li+ in the second stage.

High-performance Sn/Carbon Composite Anodes Derived from Sn(II) Acetate/Polyacrylonitrile Precursors by Electrospinning Technology

Sn/carbon composite nanofibers with various compositions were prepared from Sn(II) acetate/polyacrylonitrile (PAN) precursors by a combination of electrospinning and carbonization methods, and their potential use as anode materials for rechargeable lithiumion batteries was investigated. The composite electrode derived from 20 wt% Sn(II) acetate/PAN precursor showed excellent electrochemical properties, including a large reversible capacity of 699 mAh g-1 and a high capacity retention of 83% in 50 cycles. Sn/carbon composite nanofibers exhibited enhanced electrochemical performance ascribing to the combination of the properties of both Sn nanoparticles (large Li storage capability) and carbon matrices (long cycle life), and therefore could be potentially used in high-energy rechargeable lithium-ion batteries.