Bong-Soo Jin

The effect of titanium in Li3V2(PO4)3/graphene composites as cathode material for high capacity Li-ion batteries

We report high capacity and rate capability of titanium-added Li3V2(PO4)3 (LVP) as a cathode material for lithium ion batteries (LIBs). Titanium-added Li3V2−xTix(PO4)3/graphene (Ti-added LVP/graphene, x = 0, 0.01, 0.03, and 0.05) composites were synthesized through a sol–gel route by using titanium dioxide (TiO2) and graphene to improve the electrochemical performance. The addition of graphene and titanium significantly enhanced the electric conductivity, resulting in higher kinetic behavior of the LVP. This led to the higher specific capacity of 194 mA h g−1 at 0.1 C in the potential range of 3.0–4.8 V. The effect of graphene and Ti atoms in Ti-added LVP/graphene was investigated through physical and electrochemical measurements.

Enhanced electrochemical performance of Li3V2(PO4)3/Ag–graphene composites as cathode materials for Li-ion batteries

In this study, we have synthesized a Li3V2(PO4)3/Ag–graphene (LVP/Ag–G) composite using a facile sol–gel route. The physical and electrochemical properties of the LVP/Ag–G composite have been evaluated by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy and electrochemical measurements. In the potential range 3.0–4.3 V, the LVP/Ag–G electrode delivered a capacity of 135 mA h g−1 at a rate of 0.1 C, which is above the theoretical capacity (133 mA h g−1). Even at a high current rate of 10 C, it still exhibited a discharge capacity of 118 and 133 mA h g−1 in the potential ranges 3.0–4.3 and 3.0–4.8 V, respectively. Such a capacity value is significantly higher than previously reported works. The LVP/Ag–G composites exhibited an outstanding specific capacity, rate capability and cycling stability. These exceptional properties of the LVP/Ag–G composites were mainly attributed to the synergetic effect of the graphene and the silver particles.

Improved electrochemical performance of doped-LiNi0.5Mn1.5O4 cathode material for lithium-ion batteries

In this paper, the electrochemical performance of doped-LiNi0.5Mn1.5O4 is reviewed. The rate capability, rate performance, and cyclic life of the doped-LiNi0.5Mn1.5O4 materials with various elements are reported. The Fe, Scsubstituted materials exhibited remarkably superior cycling performance and rate capabilities than pristine LiNi0.5Mn1.5O4.

Electrochemical Characteristics of Lithium Transition-Metal Oxide as an Anode Material in a Lithium Secondary Battery

Lithium transition-metal oxides (LiTMOs) such as LiCoO2 and LiMn2O4 were investigated for their use as anode material for the lithium secondary battery. Ni¦Li0¦LiPF6(lM, EC + DEC (1 : l))¦LiTMO¦Cu cell was fabricated and its electrochemical properties were examined. LiCoO2 and LiMn2O4 showed fairly good characteristics as anode material as well as cathode material. At the 1st cathodic process, LiCoO2 had a potential plateau at 1.4 V on open circuit potential line, but LiMn2O4 had two ambiguous potential plateaus between 0.6 and 0.1 V. The specific resistance of Li¦LiCoO2 cell was 8 ohm-g, but that of Li¦LiMn{si2}O{si4} cell decreased gradually while the reaction proceeded. The specific capacities of Li¦LiCoO2 and Li¦LiMn2O4 cells at the 1st discharge were about 300 mAh/g. Capacity retention of Li¦ LiMn2O4 cell during charge-discharge cycling was higher than that of Li¦LiCoO2 cell.

Ionic conductivities of cross-linked polymer electrolytes prepared from oligo(ethylene glycol) dimethacrylates

Abstract Cross-linked polymer electrolytes are prepared from oligo(ethylene glycol) dimethacrylates (OEGDMA) with different ethylene oxide repeating units in the presence of lithium perchlorate as a lithium salt, ethylene carbonate–propylene carbonate as a mixed plasticizer, and poly(ethylene oxide) as a polymer matrix. The ionic conductivities of polymer electrolytes increase with an increasing amount of the ethylene oxide repeating unit in the OEGDMA. Conversely, the glass transition temperatures of the polymer electrolytes decrease with an increasing amount of the unit. The increased ionic conductivity can be explained by the sites of the spaces surrounded by the main chains and the cross-linking spacers in the polymers.

A study on carbon coating to silicon and electrochemical characteristics of Si-C/Li cells

The aim of this paper is to study the electrochemical behavior of Si-C material synthesized by heating a mixture of silicon and polyvinylidene fluoride (PVDF) in the ratios of 5, 20, and 50 wt%. The particle size of the synthesized material was found to be increased with increase in the PVDF ratio. The coexistence of silicon with carbon was confirmed from the XRD analysis. A field emission scanning electron microscope (FESEM) study performed with the material proved the improvement in coating efficiency with increase in the PVDF ratio. Coin cells of the type 2025 were made by using the synthesized material, and the electrochemical properties were studied. An electrode was prepared by using the developed Si-C material. Si-C|Li cells were made with this electrode. A charge|discharge test was performed for 20 cycles at 0.1 C hour rate. Initial charge and discharge capacities of Si-C material derived from 20 wt% of PVDF was found to be 1,830 and 526 mAh|g, respectively. Initial charge/discharge characteristics of the electrode were analyzed. The level of reversible specific capacity was about 216mAh/g at Si-C material derived from 20 wt% of PVDF, initial intercalation efficiency (IIE), intercalation efficiency at initial charge/discharge, was 68%. Surface irreversible specific capacity was 31 mAh/g, and average specific resistance was 2.6 ohm * g.

Optimization of Lithium in Li 1+x [Mn 0.720 Ni 0.175 Co 0.105 ]O 2 as a Cathode Material for Lithium Ion Battery

Different amounts of excess li thium in the range of x = 0~0.3 were added to Li1+x[Mn0.720Ni0.175Co0.105]O2 cathode materials synthesized using the co-precipitation method to investigate its microstructure and electrochemical properties. Pure layered structure without impurities was confirmed in the XRD pattern analysis and increasing peak intensity of Li2MnO3 was observed along with the addition of over 0.2 mol Li. The initial discharge capacity of the stoichiometric composition was determined to be 246 mAh/g, while the discharge capacity of the addition of 0.1 mol Li was obtained to be 241 mAh/g, which was not significantly different from that of the stoichiometric composition. However, the discharge capacities decreased dramatically after the addition of 0.2 and 0.3 mol Li to 162 mAh/g and 146 mAh/g, respectively. In the rate capability test, the active Li1+x[Mn0.720Ni0.175Co0.105]O2 cathode material of the stoichiometric composition showed a dramatic decrease in its discharge capacity with increasing C-rate, as evidenced by the result that the discharge capacity at 5C was 13% compared with 0.1C. On the other hand, the discharge capacity of compositions containing excess lithium was improved at higher current rates. The cycling test showed that the composition containing an excess of 0.1 mol Li had the most outstanding capacity retention.

Characterization of TiS2 composite cathodes with solid polymer electrolyte

Abstract A TiS 2 composite cathode for lithium polymer battery was developed. We investigated the a.c. impedance response as a function of temperature and charge/discharge cycling process and charge/discharge characteristics of TiS 2 composite/solid polymer electrolyte/Li cells. The passivation layer resistance of the Li/solid polymer electrolyte interface at 25 °C was 292 Ω cm 2 . The total resistance of the TiS 2 bulk and the TiS 2 /solid polymer electrolyte interfaces was 96 Ω cm 2 . The cell resistance significantly decreased at 60 °C. The discharge capacity of the TiS 2 composite cathode with 40 wt.% solid polymer electrolyte was 173 and 146 mAh/g based on TiS 2 at cycle nos. 1 and 20 at 25 °C, respectively. The utilization TiS 2 at the discharge processes nos. 1 and 20 at 25 °C were 72 and 61%, respectively. TiS 2 composite cathode with 40 wt.% solid polymer electrolyte showed better capacity with cycling.

The Electrochemical Performance of Li 3 V 2 (PO 4 ) 3 /Graphene Nano-powder Composites as Cathode Material for Li-ion Batteries

The Li3V2(PO4)3/graphene nano-particles composite was successfully synthesized by a facile sol-gel method. The addition of a graphene in Li3V2(PO4)3(LVP) showed the high crystallinity and influenced the morphology of the Li3V2(PO4)3 particles observed in X-ray diffraction (XRD) and scanning electron microscopy (SEM). The LVP/graphene samples were well connected, resulting in fast charge transfer. The effect of the addition graphene nano-particles on electrochemical performance of the materials was investigated. Compared with the pristine LVP, the LVP/graphene composite delivered a higher discharge capacity of 122 mAh g �1 at 0.1 C-rate, better rate capability and cyclability in the potential range of 3.04.3 V. The electrochemical impedance spectra (EIS) measurement showed the improved electronic conductivity for the LVP/graphene composite, which can ensure the high specific capacity and rate capability.

Electrochemical Properties of 0.3Li 2 MnO 3 ·0.7LiMn 0.55 Ni 0.30 Co 0.15 O 2 Electrode Containing VGCF for Lithium Ion Battery

The 0.3Li2MnO3·0.7LiMn0.55Ni0.30Co0.15O2 cathode material was prepared via a co-precipitation method. The vapor grown carbon fiber (VGCF) was used as a conductive material and its effects on electrochemical properties of the 0.3Li2MnO3·0.7LiMn0.55Ni0.30Co0.15O2 cathode material were investigated. From the XRD pattern, the typical complex layered structure was confirmed and a solid solution between Li2MnO3 and LiMO2 (M = Ni, Co and Mn) was formed without any secondary phases. The VGCF was properly distributed between cathode materials and conductive sources by a FE-SEM. In voltage profiles, the electrode with VGCF showed higher discharge capacity than the pristine electrode. At a 5C rate, 146 mAh/g was obtained compared with 232 mAh/g at initial discharge in the electrode with VGCF. Furthermore, the impedance of the electrode with VGCF did not changed much around 9-10 Ω while the pristine electrode increased from 21.5 Ω to 46.3 Ω after the 30 charge/discharge cycling.