• Journal of Electrochemical Science and Technology
• /
• v.4 no.3
• /
• pp.113-118
• /
• 2013

Fluorophosphate, $Na_2MnPO_4F$ as new cathode material was synthesized by carbothermal treatment method. Prepared $Na_2MnPO_4F$ has particle size under 100 nm and residual carbon exists in surface of $Na_2MnPO_4F$. Additional carbon coating was performed in order to increase the electrochemical properties. Even capacity and overpotential were improved by carbon coating using mechanical ball milling, the reduced crystallinity limited the drastic improvement of the electrochemical properties. To solve this problem, re-heat treatment was involved to recover crystallinity and then notable improvement of electrochemical properties was obtained. Specific amount of $Li^+$ that participates in electrochemical $Li^+$ insertion / extraction reaction, was x = 1 in $Li_xNa_{2-x}MnPO_4F$ within the voltage range of 2.0 to 4.8 V. The doubled capacity by 2 electron reaction can be obtained when NMPF is charged to higher voltage over 4.8 V.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.11a
• /
• pp.132-132
• /
• 2009

Phospho-olivine $LiFePO_4$ cathode materials were prepared by hydrothermal reaction. In this study, Multi-walled carbon nanotube (MWCNT) and Carbon black was added to enhance the electrical conductivity of $LiFePO_4$. $LiFePO_4$, $LiFePO_4$-MWCNT and $LiFePO_4$-C particles were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) transmission electron microscope (TEM). $LiFePO_4/SPE/Li$, $LiFePO_4$-MWCMT/SPE/Li and $LiFePO_4$-C/SPE/Li cells were characterized electrochemically by charge/discharge experiments at a constant current density of $0.1mA\;cm^{-2}$ in a range between 2.5 and 4.3 V vs. $Li/Li^+$ and cyclic voltammetry (CV).

• Journal of the Mineralogical Society of Korea
• /
• v.22 no.1
• /
• pp.63-72
• /
• 2009

Carbon-coated lithium iron phosphate ($LiFePO_4/C$) composites are synthesized by the modified mechanical activation method (modified MA process) and studied by the Rietveld structural refinement. Rietveld indices of $LiFePO_4/C$ indicate good fitting with $R_p=8.14%,\;R_{wp}=11.1%,\;R_{exp}=9.09%,\;R_B=3.88%$, and S (GofF, Goodness of fit) = 1.2, respectively. $LiFePO_4/C$ with a space group Pnma shows a = 10.3229(3)${\AA}$, b = 6.0052(2) ${\AA}$, c = 4.6939(1) ${\AA}$, and V = 290.98(1) ${\AA}^3$ in dimension, indicating good agreements with those of previous works. Synthetic powders are nano-sized ($65{\sim}90nm$) homogeneous particles with high purity. Thus the modified MA method will be an efficient process to get a high quality cathode material for commercial lithium batteries.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.11a
• /
• pp.316-316
• /
• 2007

리튬폴리머 전지용 정극활물질인 $LiFePO_4$를 수열법으로 합성하였다. 제조한 정극활물질 $LiFePO_4$는 X-ray 회절분석을 통하여 olivine 구조임을 확인하였다. 전극 제조 시 첨가된 도전재의 종류에 따른 전기화학적 특성변화를 알기 위하여, Acetylene Black, Super-Black, Multi-Walled Carbon Nanotube(MWCNT), SP270을 도전재로 제조된 정극활물질과 PVDF를 결합제로 사용하였다. 셀은 제조된 정극과 고체전해질 $25PVDFLiCIO_4EC_{10}PC_{10}$를 사용하고, 부극은 금속리튬으로 coin 타입의 cell을 조립하여 충방전을 진행하였다. 충방전 진행결과, Multi-Walled Carbon Nanotube(MWCNT)를 도전재로 사용하였을 경우, 초기 방전용량은 94mAh/g, 100cycle 후에는 약 93mAh/g인 기타 도전재를 사용하였을 때보다 안정하고 높은 방전용량을 나타내었다. 이때의 충방전 전류밀도는 0.1mAh/g이고 전압범위 는 2.5~4.3V이었다.

• Journal of the Korean Magnetics Society
• /
• v.17 no.2
• /
• pp.65-70
• /
• 2007

In this paper, we composed the $LiFePO_4$ for the reversible use as the replacement material of the Li ion batteries and confirmed the good quality of the structure of the samples with the sintering temperature $675^{\circ}C,\;750^{\circ}C,\;and\;800^{\circ}C$ for 30 hours at nitrogen atmosphere. We also investigated the size of the particles through SEM picture and the change of the sintering temperature and the $Fe^{+3}$ content after charging the materials with 1 V, 160 mA and 3 V, 40 mA for 3 hours by Mossbauer spectroscopy. Also we can observe the increase on the $Fe^{+3}$ content at the charge condition and the increase of the amount ratio of the $Fe^{+3}$ ion only in sintering temperature $675^{\circ}C$ according to the increase of the electric charge. We cannot observe the change of the $Fe^{+3}$ ion in sintering temperature $800^{\circ}C$ after charging.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1999.11a
• /
• pp.159-162
• /
• 1999

All solid state thin film micro-batteries consisting of lithium metal anode, an amorphous LiPON electrolyte and cathode of vanadium oxide have been fabricated and characterized, which were fabricated with cell structure of Li/LiPON/V$_2$O$\sub$5/Pt. The vanadium oxide thin films were formed by d.c. reactive sputtering on Pt current collector. After deposition of vanadium oxide films, in-situ growths of lithium phosphorus oxynitride film were conducted by r.f. sputtering of Li$_3$PO$_4$ target in mixture gas of N$_2$ and O$_2$. The pure metal lithium film was deposited by thermal evaporation on thin film LiPON electrolyte. The cell capacity was about 45${\mu}$Ah/$\textrm{cm}^2$ $\mu\textrm{m}$ after 200 cycle. No appreciable degradation of the cell capacity could be observed after 50 cycles .