Quanchao Zhuang

Electrochemical and electronic properties of LiCoO2 cathode investigated by galvanostatic cycling and EIS

The processes of extraction and insertion of lithium ions in LiCoO(2) cathode are investigated by galvanostatic cycling and electrochemical impedance spectroscopy (EIS) at different potentials during the first charge/discharge cycle and at different temperatures after 10 charge/discharge cycles. The spectra exhibit three semicircles and a slightly inclined line that appear successively as the frequency decreases. An appropriate equivalent circuit is proposed to fit the experimental EIS data. Based on detailed analysis of the change in kinetic parameters obtained from simulating the experimental EIS data as functions of potential and temperature, the high-frequency, the middle-frequency, and the low-frequency semicircles can be attributed to the migration of the lithium ions through the SEI film, the electronic properties of the material and the charge transfer step, respectively. The slightly inclined line arises from the solid state diffusion process. The electrical conductivity of the layered LiCoO(2) changes dramatically at early delithiation as a result of a polaron-to-metal transition. In an electrolyte solution of 1 mol L(-1) LiPF(6)-EC (ethylene carbonate) :DMC (dimethyl carbonate), the activation energy of the ion jump (which is related to the migration of the lithium ions through the SEI film), the thermal activation energy of the electrical conductivity and the activation energy of the intercalation/deintercalation reaction are 37.7, 39.1 and 69.0 kJ mol(-1), respectively.

Phosphorus and oxygen dual-doped graphene as superior anode material for room-temperature potassium-ion batteries

The intercalation of potassium ions into graphitic carbon materials has been demonstrated to be feasible while the electrochemical performance of the potassium-ion battery (PIB) is still unsatisfactory. More effort should be made to improve the specific capacity and achieve superior rate capability. Functional phosphorus and oxygen dual-doped graphene (PODG) is introduced as the anode for PIB, made by a thermal annealing method using triphenylphosphine and graphite oxide as precursors. It exhibits high specific capacity and ultra-long cycling stability, delivers a capacity of 474 mA h g−1 at 50 mA g−1 after 50 cycles and retains a capacity of 160 mA h g−1 at 2000 mA g−1 after 600 cycles. The superior electrochemical performance of PODG is mainly due to the large interlayer spacing caused by phosphorus and oxygen dual-doping, which facilitates potassium-ion insertion and extraction. Furthermore, the ultrathin and wrinkled features structure leads to a continuous and efficient supply of vacancies and defects for potassium storage.

Synthesis and characterization of pristine Li2MnSiO4 and Li2MnSiO4/C cathode materials for lithium ion batteries

The cathode materials, pristine Li2MnSiO4 and carbon-coated Li2MnSiO4 (Li2MnSiO4/C), were synthesized by the sol–gel method. Power X-ray diffraction and scanning electron microscopy analyses show that the presence of carbon during synthesis can weaken the formation of impurities in the final product and decrease the particle size of the final product. The effects of carbon coating on electrochemical characteristics were investigated by galvanostatic cycling test and electrochemical impedance spectroscopy. The galvanostatic cycling test results indicate that Li2MnSiO4/C cathode exhibits better electrochemical performance with an initial discharge capacity of 134.4 mAh g−1 and a capacity retention of 63.9 mAh g−1 after 20 cycles. Electrochemical impedance analyses confirm that carbon coating can increase electronic conductivity, which results in good electrochemical performance of Li2MnSiO4/C cathode. The two semicircles and the large arc obtained in this study can be attributed to the migration of lithium ions through the solid electrolyte interphase films, the electronic properties of the material, and the charge transfer step, respectively.

Co2+xTi1−xO4 nano-octahedra as high performance anodes for lithium-ion batteries

Single crystal Co2+xTi1−xO4 nano-octahedra enclosed by {111} planes with an average edge length of 200 nm were synthesized via a one-step hydrothermal approach using economical TiO2 as a titanium source. The structure of Co2+xTi1−xO4 is actually an inverse spinel solid solution with an excess amount of Co. As anode materials for lithium-ion batteries (LIBs), the Co2+xTi1−xO4 electrode delivered a high specific capacity of over 766.5 mA h g−1 at the current density of 100 mA g−1 after 60 cycles; moreover, it provided stable rate capability and lithium storage performance at the high current density of 680 mA h g−1 after 400 cycles at 1000 mA g−1. This excellent electrochemical performance is mainly derived from the atomic-level combination of two active materials (CoO and TiO2 matrix) via different lithium storage mechanisms (conversion reaction and insertion/extraction, respectively) after the initial discharge process. In particular, the nanostructured TiO2 matrix formed after the first cycle in the electrode would alleviate large volume changes and avoid rapid capacity fading, which could endow Co2+xTi1−xO4 electrodes with excellent structural stability.

CHISELED NICKEL HYDROXIDE NANOPLATES GROWTH ON GRAPHENE SHEETS FOR LITHIUM ION BATTERIES

National Basic Research Program of China [2009CB220102]; National Natural Science Foundation of China [51221462]; Jiangsu Ordinary University Graduate Innovative Research Programs [CXZZ12_0943]; Jiangsu Planned Projects for Postdoctoral Research Funds [1201030C]; Priority Academic Program Development of Jiangsu Higher Education Institutions

Tertiary butyl hydroquinone as a novel additive for SEI film formation in lithium-ion batteries

Electrolyte additives play a key role in the performance of lithium ion batteries. In this study, we reported tertiary butyl hydroquinone (TBHQ) as a new electrolyte additive with a promising prospect. It largely improved the electrochemical performance of the graphite electrode such as cyclic stability and reversible capacity. The improvement was benefited from the effective formation of a stable and compact thin solid–electrolyte-interface (SEI) film to reduce the resistance. Thus, this study demonstrated a promising electrolyte additive for improving lithium-ion battery performance.

Electrochemical behavior of α-MoO3 nanobelts as cathode material for lithium ion batteries

Abstractα-MoO3 nanobelts were synthesized by simple hydrothermal method and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Cyclic voltammogram (CV) and galvanostatic charge/discharge testing techniques were employed to evaluate electrochemical behaviors of α-MoO3 materials. Results showed that α-MoO3 nanobelts with about 80 nm in diameter and 5–12 μm in length were grown in the orthorhombic system. Electrochemical characterisation confirmed that in lithium ion insertion/extraction process, the first intercalation of lithium ion in α-MoO3 at about 2.8 V was irreversible, corresponding to LixMoO3 (0 < x ≤ 0.25) and the parent MoO3 materials coexisting, the second lithium ion inter-calation was reversible at the potential range of 2.2–2.4 V followed by LixMoO3 (0.25 < x ≤ 0.5), and below 1.0 V the mechanism of lithium ion storage changed from lithium ion intercalation reaction into lithium alloying reaction. The α-MoO3 nanobelts showed better electrochemical performance, 319 mA h g−1 initial discharge capacity, around 52% capacity retention after 20 cycles than that of α-MoO3 bulk.

Synthesis and the comparative lithium storage properties of hematite: hollow structures vs. carbon composites

In the present work, α-Fe2O3 hollow structures from nanotubes to nanorings, and α-Fe2O3/carbon composites composed of nanoparticles homogeneously dispersed on graphene sheets and carbon nanotubes were synthesized via self-assembly combined with a facile hydrothermal method, and their structure, morphology and electrochemical performance were characterized by XRD, XPS, SEM, TEM, CV, charge–discharge tests and EIS. The focus is elucidating how structural aspects, such as particle size and shape of the nanoparticles as well as the carbon matrix, influence the electrochemical properties of the α-Fe2O3 nanoparticles. The results revealed that the cycling performance of hollow structured α-Fe2O3 improves with the increase of aspect ratio, namely, the α-Fe2O3 nanotubes exhibit the best electrochemical performance in terms of reversible capacity, capacity retention and rate performance, which is comparable to that of α-Fe2O3 nanoparticle–carbon composites. It is expected that the synthesis of α-Fe2O3 nanotubes with high aspect ratio anchored on conducting graphene would be a potential anode material for high performance LIBs.

FACILE SYNTHESIS OF MAGNETITE/CARBON NANOTUBES NANOCOMPOSITES WITH STABLE AND RATE CAPABILITY AS ANODE MATERIALS FOR LITHIUM-ION BATTERIES

Fe3O4/carbon nanotubes (CNTs) nanocomposites are successfully prepared by a facile hydrothermal method, without any reducing agents. SEM shows that the CNTs are dispersed well in the Fe3O4 nanoparticles of 50 to 100nm in size. The electrochemical properties of the prepared nanocomposites as anode materials are further evaluated by galvanostatic charge/discharge cycling and

Phosphorus Particles Embedded in Reduced Graphene Oxide Matrix to Enhance Capacity and Rate Capability for Capacitive Potassium-Ion Storage

Early studies indicate that graphite is feasible as the negative electrode of a potassium-ion battery, but its electrochemical performance still cannot meet the demands of applications. More efforts should be focused on increasing the specific capacity and improving the rate capability in the meantime. Thus, stainless-steel autoclave technology has been utilized to prepare phosphorus nanoparticles encapsulated in reduced graphene oxide matrix as the electrode materials for a potassium-ion battery. As a result, the composite matrix affords high reversible capacities of 354 and 253 mA h g-1 at 100 and 500 mA g-1 , respectively. The superior electrochemical performance is mainly because the composite matrix possesses better electronic conductivity and a robust structure, which can promote the electron-transfer performance of the electrode. Furthermore, phosphorus particles can contribute to the high capacity through an alloying mechanism. In addition, the silklike, ultrathin, film composite with a high surface area is conducive to capacitive potassium-ion storage, which plays a more important role in rate performance and a high current density capability.