Qizhen Xiao

A capsule-type gelled polymer electrolyte for rechargeable lithium batteries

A trilayer fibrous membrane was integrated by cross-linked PMMA (CL-PMMA) to form a blended fibrous membrane. Owing to encapsulation of the CL-PMMA component, the resultant gelled polymer electrolyte shows high thermal stability, good electrolyte retention and high ionic conductivity, which is suitable for rechargeable lithium batteries.

Hybrid LiV3O8/carbon encapsulated Li1.2Mn0.54Co0.13Ni0.13O2 with improved electrochemical properties for lithium ion batteries

A low coulombic efficiency in the first cycle and poor rate capability limit the practical application of a lithium rich manganese-based solid solution (LMSS) in lithium ion batteries. To resolve these problems, a core–shell type of Li1.2Mn0.54Co0.13Ni0.13O2@LiV3O8/C (LMSSVC) composite material was prepared using a sol–gel process, in which NH4VO3-derived V2O5 chemically leached lithium from the LMSS and formed the LiV3O8 during high temperature annealing. The effect of the hybrid LiV3O8/C layer on the electrochemical properties of the LMSS is investigated using cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge–discharge measurements. The as-prepared LiV3O8 nanoparticles are embedded within the carbon matrix uniformly, which becomes an outer shell to encapsulate the LMSS nanoparticles. Because of the Li-host nature of LiV3O8 and the electronic conductivity of carbon, the LMSSVC can deliver a capacity of 269 mA h g−1 at a 0.1C rate in the first cycle over the voltage range of 2.0–4.8 V together with a coulombic efficiency of 94%, and retain 94% of the initial capacity after 50 cycles. It can deliver capacities of 258, 245, 229, 207 and 176 mA h g−1 at the rates of 0.2C, 0.5C, 1C, 2C and 5C, respectively. The results indicate that surface coating of the hybrid LiV3O8/C layer can improve not only the initial coulombic efficiency but also the rate capability of the LMSS material.

High performance Li1·2(Mn0·54Co0·13Ni0·13)O2 with AlF3/carbon hybrid shell for lithium ion batteries

Abstract A kind of core shell cathode material, Li1·2(Mn0·54Co0·13Ni0·13)O2@AlF3/C (LMSAC) was prepared by coating AlF3 and carbon hybrid layer on the surface of lithium rich manganese based solid solution (LMSS) through a sol–gel process. It was characterised by X-ray diffraction (XRD) patterns, scanning electron microscope (SEM) and transmission electron microscope (TEM). Its electrochemical properties were evaluated by electrochemical impedance spectra and galvanostatic charge–discharge measurements. Owing to the AlF3/C shell, the LMSAC could deliver the initial capacities of 278, 260, 246, 230 and 210 mAh g−1 at the rates of 0·1, 0·2, 0·5, 1 and 2C in the potential range of 2–4·8 V (versus Li+/Li) respectively, exhibiting an excellent rate capability. The corresponding coulombic efficiencies are 90, 89, 87, 88 and 85% in the first cycle. After cycled at the 0·1C and 1C rates for 50 times, the LMSAC remains 97 and 96% of the initial capacities respectively, displaying an enhanced cycling performance. The results suggest that surface coating of AlF3/C hybrid layer could be a promising method to improve the electrochemical properties of the LMSS cathode materials.

Embedding of Mg-doped V2O5 nanoparticles in a carbon matrix to improve their electrochemical properties for high-energy rechargeable lithium batteries

Hierarchical Mg-doped V2O5@carbon (HVC) spheres were fabricated using poly(methacrylic acid) (PMAA) microgel as a microreactor. The monodisperse micron-sized spheres are formed from 200 nm particles, in which primary V2O5 nanoparticles are embedded uniformly in a carbon matrix to form a mulberry-like morphology. The effect of the Mg-doping level on the electrochemical properties of the as-prepared HVC spheres was studied. Benefitting from the unique morphology and chemical pre-insertion of Mg2+ ions, the Mg0.10V2O5@C sample exhibited an excellent rate capability and stable cyclability when operated over the potential range of 1.5–4.0 V (vs. Li+/Li). The results suggest that these porous HVC spheres hold promise for use as high-energy-density cathode materials for rechargeable lithium batteries.

AlPO4-coated V2 O5 nanoplatelet and its electrochemical properties in aqueous electrolyte

Abstract Vanadium pentoxide (V2 O5) nanoplatelet was prepared through an exfoliation method by using β-cyclodextrin (β-CD) as intercalating template. To improve its electrochemical performance in the aqueous electrolyte, the nanoplatelet was coated with amorphous AlPO4 by sol-gel method. The effect of this coating layer on the rate and cycling properties is investigated by cyclic voltammetry and galvanostatic charge-discharge. The 1.6 % AlPO4-coated sample could deliver an initial capacity of 128 mAh g–1 at 0.1 C rate, and remain 99 % of the initial one after 50 cycles. The discharge capacities in the first cycle are 119, 113, and 104 mAh g–1 at the rates of 0.3, 1.5, and 3 C, respectively. The corresponding maintaining ratios are 98, 92, and 87 % after 50 cycles. The results suggest the AlPO4-coated V2 O5 nanoplatelet has good rate capability and cycling performance, indicating its promising application as an anode material in aqueous rechargeable lithium batteries.