• Applied Chemistry for Engineering
• /
• v.25 no.6
• /
• pp.592-597
• /
• 2014

The graphite/$SiO_2$ composites as anode materials for lithium-ion batteries were prepared by sol-gel method to improve the graphite's electrochemical characteristics. The prepared graphite/$SiO_2$ composites were analysed by XRD, FE-SEM and EDX. The graphite surface modified by silicon dioxide showed several advantages to stabilize SEI layer. The electrochemical characteristics were investigated for lithium ion battery using graphite/$SiO_2$ as the working electrode and Li metal as the counter electrode. Electrochemical behaviors using organic electrolytes ($LiPF_6$, EC/DMC) were characterized by charge/discharge, cycle, cyclic voltammetry and impedance tests. The lithium ion battery using graphite/$SiO_2$ electrodes had better capacity than that of using graphite electrodes and was able to deliver a discharge capacity with 475 mAh/g at a rate of 0.1 C. Also, the capacity retention ratio of the modified graphite reaches 99% at a rate of 0.8 C.

• Journal of IKEEE
• /
• v.27 no.4
• /
• pp.477-485
• /
• 2023

In this paper, the effect of AC ripple on the lifetime of lithium-ion batteries is experimentally analyzed. Bidirectional power conversion system(PCS) is used to increase the efficiency of energy storage systems (ESS). When connected to the grid, a current ripple with a frequency twice the grid frequency is applied to the battery due to its structure. Therefore, to analyze the effect of AC ripple on Li-ion battery aging, cycle life test are performed by applying charge/discharge profiles of DC current and DC+AC current ripple specifications. Based on the experimental results, direct current internal resistance (DCIR), incremental capacitance (IC), and surface temperature were analyzed. As a result, it is confirmed that AC ripple does not directly affect degradation and that battery degradation slows down after a certain cycle. These results can serve as a guideline for optimizing filters to reduce ripple on the battery side in applications where AC ripple occurs.

• Journal of the Korean Chemical Society
• /
• v.37 no.5
• /
• pp.491-495
• /
• 1993

Synthesis of polymer-supported azacrown ether ion exchanger, {(4,5): (13,14)-dibenzo-6,9,12-trioxa-3,15,21-triazazabicyclo[15.3.1]heneicosa-1(21),17,19-triene-2,16-dione : DBPDA ion exchanger}, and its ion binding ability to alkali metal $(Li^+,\;Na^+,\;K^+)$ picrates were studied. The binding constants $(K_b)$ of DBPDA ion exchanger to the alkali metal picrates in ether type solvents were obtained by spectrophotometry. Binding constants of alkali metal ions were in the order to Li < Na < K, and alkali metal ions were formed 1 : 1 complexes with ligands of DBPDA ion exchanger. Also, $K_b$ was found to depend on the variables such as solvent and temperature. The binding constants for the complexes were obtained in the ranges of $2{\times}10^3{\sim}4{\times}10^4M^{-1}$. In order to obtain the enthalpy (${\Delta}$H) and entropy changes (${\Delta}$S)n the complexation process, Kb were plotted against the temperature in the ranges of 10∼40$^{\circ}C$ according to the van't Hoff theory. Enthalphy and entropy changes were found in the ranges of -2.71∼-3.79 kcal/mol, and -16.52∼-20.57 eu, respectively.

• Journal of the Korean Ceramic Society
• /
• v.38 no.11
• /
• pp.1055-1059
• /
• 2001

Porous glass ceramics composed of Li$_2$O.-Ti $O_2$-P$_2$ $O_{5}$ -CaO were prepared by melting and 2 step heat treatment for nucleation at 61$0^{\circ}C$ and crystallization at 78$0^{\circ}C$. subsequently $\beta$-Ca$_3$(P $O_4$)$_2$crystal phase was selectively leached out in 1N-HC1 solution for 3 days, leaving Li $Ti_2$(P $O_4$)$_3$crystal phases. prepared porous glass ceramics were immersed in 1M AgN $O_3$solution for ion exchange. Staphylococcus aureus and salmonella typhi were used in this study. It was found taht the resultant porous glas ceramics show excellent bacteriostatic properties.

• Journal of Electrochemical Science and Technology
• /
• v.14 no.3
• /
• pp.293-300
• /
• 2023

The global energy storage markets have gravitated to high-energy-density and low cost of lithium-ion batteries (LIBs) as the predominant system for energy storage such as electric vehicles (EVs). High-Ni layered oxides are considered promising next-generation cathode materials for LIBs owing to their significant advantages in terms of high energy density. However, the practical application of high-Ni cathodes remains challenging, because of their structural and surface instability. Although extensive studies have been conducted to mitigate these inherent instabilities, a two-step process involving the synthesis of the cathode and a dry/wet coating is essential. This study evaluates a one-step β-Li₂SnO₃ layer coating on the surface of LiNi_0.8Co_0.2O₂ (NC82) via the thermal segregation of Sn owing to the solubility limit with respect to the synthesis temperature. The doping, segregation, and phase transition of Sn were systematically revealed by structural analyses. Moreover, surface-engineered 5 mol% Sn-coated LiNi_0.8Co_0.2O₂ (NC82_Sn5%) exhibited superior capacity retention compared to bare NC82 owing to the stable surface coating layer. Thus, the developed one-step coating method is suitable for improving the properties of high-Ni layered oxide cathode materials for application in LIBs.

• Journal of Powder Materials
• /
• v.10 no.1
• /
• pp.21-25
• /
• 2003

The Sn - graphite composites were prepared by chemical encapsulation method for anode materials in Li-ion batteries. EDS and XRD analysis confirmed the presence of Sn in the graphite structure. Cyclic voltammometry (CV) measurement shows extra reduction and oxidation peaks, which might to be related to the formations of $Li_xSn$ alloy compounds. Graphite-tin composite electrodes demonstrated higher Lithium storage capacities than graphite electrodes. Due to the nature of fine Sn particles on graphite surface, the graphite-tin composite electrodes have shown a good cycle properties.

• Proceedings of the Polymer Society of Korea Conference
• /
• 2006.10a
• /
• pp.187-187
• /
• 2006

A new type solid polymer electrolyte (SPE) composed of poly (vinyl alcohol) (PVA) and lithium trifluoromethanesulfonate ($LiCF_{3}SO_{3}$) was prepared by means of the solution cast technique to observe that Li ion can move by ion hopping decoupled from polymer segmental motion inside of the 'fast cationic transport process'. The highest ion conductivity of the SPEs obtained from ac impedance measurements was $1.42{\times}10^{-3}S/cm$ at room temperature for SPE with 80wt% of salt concentration. Using LSV, we found that the SPEs had good electrochemical stabilities and using FT-IR and AFM, we found the formation of network-like structure.

• Korean Journal of Materials Research
• /
• v.16 no.5
• /
• pp.297-301
• /
• 2006

Si/Mo multilayer anode consisting of active/inactive material was prepared using rf/dc magnetron sputtering. Molybdenum acts as a buffer against the volume change of the Silicon. Multilayer deposited on RT (reversible treatment) copper foil current collector to enhance adhesion between Silicon and copper foil. Deposited Silicon was identified as an amorphous. Amorphous has a relatively open structure than crystal structure, thus prevents the lattice expansion and has many diffusion paths of Li ion. When deposited time of Silicon and Molybdenum is 30 second and 2 second respectably, electrode has more capacity and good cycle stability. A 3000 nm thick multilayer was maintained 99% of the initial capacity (1624 $mAhg^{-1}$) after 100 cycles. As the increase of the multilayer thickness (4500 nm, 6000 nm), Si/Mo mutilayer anodes show aggravation cycle stability.

• Proceedings of the KSRS Conference
• /
• 2008.10a
• /
• pp.96-99
• /
• 2008

The MRE (Monitoring Reconfiguration Electronics) board included inside the SCU (Spacecraft Computer Unit) in the COMS (Communication, Ocean and Meteorological Satellite) spacecraft is used to monitor the battery voltage and to detect a battery under voltage (low battery capacity) or a battery overvoltage (overcharge). In case of alarm detection, a reconfiguration is initiated by the MRE board. The MRE configures the overall spacecraft in the survival mode to protect the Li-Ion (lithium ion) battery from overcharge and over discharge. For the EPS (Electrical Power Subsystem) point of view, the survival mode can be trigged from hardware wired thresholds. The aim of this paper to provide and to justify the low and high threshold levels which are associated to the MRE battery voltage monitoring. The MRE trig guarantees minimum battery energy to available for the required 48 hours autonomy duration of the spacecraft after MRE trig in the survival mode.

• Carbon letters
• /
• v.11 no.4
• /
• pp.343-346
• /
• 2010

The various expanded graphites (EGs) was prepared and applied as anode material for high power Li-ion secondary battery (LIB). By changing the processing conditions of EG, a series of EG with different structure were produced, showing the changed electrochemical properties. The charge-discharge test showed that the initial reversible capacity of EG anodes prepared at the suitable conditions was over 400 mAh/g and the charge capacity at 5 C-rate was 83.2 mAh/g. These values demonstrated the much improved electrochemical properties as compared with those for the graphite anode of 360 mAh/g and 19.4 mAh/g, respectively, showing the possibility of EG anode materials for high power LIB.