Lu Hou

Large-scale synthesis of Li1.15V3O8 nanobelts and their lithium storage behavior studied by in situ X-ray diffraction

Li1.15V3O8 nanobelts with length 3 μm, width 200 nm and 20–50 nm in thickness are prepared on a large scale by a tartaric acid-assisted sol–gel technique. They show greater reversibility of the lithium ion insertion/extraction reaction than those synthesized without the addition of tartaric acid. After twenty cycles, the reversible lithium storage capacities of Li1.15V3O8 prepared from tartaric acid assisted and free techniques are 231.0 and 194.5 mAh/g at a current density of 30 mA g−1, respectively. Cycled at 20 mA g−1 in 1.5–4.1 V, Li1.15V3O8 nanobelts can deliver discharge and charge capacities of 297.0 and 298.4 mAh/g, respectively. Increasing the charge/discharge current density to 2400 mA g−1, the lithiation and delithiation capacities of Li1.15V3O8 nanobelts can be mantianed at 184.2 and 184.2 mAh/g, respectively. In situXRD observation reveals that the host structure of Li1.15V3O8 nanobelts will not be destroyed with a discharge process to 0.0 V at 20 mA g−1 or a short circuit for 24 h. Over-lithiation can induce the formation of an inactive compound, leading to poor electrochemical properties of Li1.15V3O8 nanobelts. The first lithiation/delithiation process in 0.0–4.1 V or 1.5–4.1 V is a reversible reaction at a current density of 60 mA g−1, and is composed of reversible single-phase structural evolutions in a high voltage region and two-phase structural transitions in a low voltage region. The electrochemical properties of Li1.15V3O8 nanobelts are poorer at the 10th cycle in 0.0–4.1 V than that obtained in 1.5–4.1 V. In situXRD results indicate that the breakdown of two-phase transition in a low voltage region is the main factor for poor cycleability. Besides, a delay of structural evolution and asymmetry lithiation/delithiation process can be observed at high rates, which may also be responsible for the deterioration of cycleability of Li1.15V3O8 nanobelts.

In situ fabrication of Li4Ti5O12@CNT composites and their superior lithium storage properties

In this paper, Li4Ti5O12@CNT composites are fabricated by a controlled in situ growth of CNTs on the surface of Li4Ti5O12. The formation of coiled CNTs occurs by the electroless loading of Ni–P catalysts on the surface of Li4Ti5O12. Coiled CNTs provide electron bridges interconnecting the Li4Ti5O12 particles to form a nano/micro-structured conductive hyper-network. The electronic conductivity of Li4Ti5O12@CNT composites is better than that of the sample before coating. As a result, Li4Ti5O12@CNT composites show superior lithium storage properties comparable to the pristine Li4Ti5O12. Based on electrochemical analysis, it is obvious that Li4Ti5O12@CNT composites can deliver reversible charge capacities of 149.2, 102.6, 73.3 and 47.5 mA h g−1 at 0.2 C, 10 C, 20 C and 50 C, respectively.

Facile preparation of nano-micro structure PbSbO2Cl as a novel anode material for lithium-ion batteries

We report the development of PbSbO2Cl as a new anode material for lithium-ion batteries. It is prepared by a simple hydrothermal method from Pb(NO3)2 and SbCl3. The as-prepared PbSbO2Cl shows a well-dispersed nano-micro structure with particle sizes of 200–500 nm. The initial discharge capacity of PbSbO2Cl is 1011.0 mAh g−1 corresponding to 14.6 Li per formula storage in the structure. In the inverse charge process, a reversible capacity of 731.8 mAh g−1 can be delivered. This suggests that PbSbO2Cl may be a promising high-capacity anode material for lithium-ion batteries.

Ex situ FTIR spectroscopy study of LiVPO4F as cathode material for lithium-ion batteries

The LiVPO4F as cathode material for lithium-ion batteries was synthesized through two steps of solid-state reactions and investigated by ex situ Fourier transform infrared (FTIR) spectroscopy for the initial charge and discharge cycle. The characterization of the effect on the structure of the LiVPO4F in the process of lithium-ion insertion/extraction at a molecular level by ex situ FTIR spectroscopy is helpful for the mechanism research for lithium-ion insertion/extraction and the improvement of the performance of lithium-ion batteries. In the process of the initial cycle, new bands of VPO4F appear in the charge and the featured bands of LiVPO4F reappear in the discharge. In this paper, ex situ FTIR spectra indicates that the structure of the LiVPO4F in the process of lithium-ion insertion/extraction is almost not affected, which clearly states that the LiVPO4F possesses stable structure as cathode material. Consequently, the LiVPO4F might be expected as a potential cathode replacement for commercial lithium-ion batteries.