• Proceedings of the Korean Magnestics Society Conference
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• 2009.05a
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• pp.29-30
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• 2009

• Proceedings of the Korean Ceranic Society Conference
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• 2003.10a
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• pp.212.1-212
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• 2003

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.216-216
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• 2003

현재 상용화되어 있는 리튬 이차전지용 양극재료로는 비교적 작동전압이 높은 층상 암염구조(LiCoO$_2$, LiNiO$_2$) 및 Spinet계(LiMn$_2$O$_4$) 전이금속 산화물이 대부분 이용되고 있다 하지만 LiCoO$_2$나 LiNiO$_2$ 같은 상용화 물질은 비교적 높은 비용과, 강한 독성 때문에 많은 문제점을 가지고 있다. 또 Spinel(LiMn$_2$O$_4$)는 낮은 비용과 환경친화적인 장점에도 불구하고 Jahn-Teller 변형과 관련된 구조적 변형이 심각하기 때문에 사이클시 비가역적인 용량의 감소가 심각하다. 이러한 관점에서 전이금속보다 그 양이 풍부하고 저렴할 뿐만 아니라 독성이 없는 Olivine 구조 (LiFePO$_4$)를 갖는 phosphate계 화합물에 관심을 가지게 되었다. LiFePO$_4$는 리튬 음극과 3.4V의 방전전압을 나타내며, 170mAh/g의 이론용량을 가지고 있어, Fe-base의 장점은 물론 안정적인 결정구조 및 현재 상용화된 재료들과 비슷한 에너지 밀도를 가진다. 따라서 본 연구에서는 양극물질의 기존 두 제조법인 고상반응법과 sol-gel법으로 대표되는 제조법의 단점을 상호 보완될 수 있다고 판단되는 기계적 합금화법(Mechanical Alloying, MA)공정을 도입하여 초미세립 분말 제조에 초점을 맞추어 Olivine phosphate계 양극물질의 제조 및 전기화학적 특성을 연구하였다.

• Journal of the Korean Electrochemical Society
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• v.19 no.3
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• pp.101-106
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• 2016

In this study, we prepared an ionic liquid composite solid polymer electrolyte (PEO-LiTFSI-$Pyr_{14}TFSI$) with poly(ethylen oxide), lithium bis(trifluoromethanesulfonyl)imide, N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide by blending-cross linking process. Although the PEO-LiTFSI-$Pyr_{14}TFSI$ composite solid polymer electrolyte displayed a small peak at 4.4 V, it had high electrochemical oxidation stability up to 5.7 V. Ionic conductivity of the PEO-LiTFSI-$Pyr_{14}TFSI$ composite solid polymer electrolyte increased with increasing temperature from $10^{-6}S\;cm^{-1}$ at $30^{\circ}C$ to $10^{-4}S\;cm^{-1}$ at $70^{\circ}C$. To investigate the electrochemical properties, the PEO-LiTFSI-$Pyr_{14}TFSI$ composite solid polymer electrolyte assembled with $LiFePO_4$ cathode and Li-metal anode. At 0.1 C-rate, the cell delivered $40mAh\;g^{-1}$ for $30^{\circ}C$, $69.8mAh\;g^{-1}$ for $40^{\circ}C$ and $113mAh\;g^{-1}$ for $50^{\circ}C$, respectively. The PEO-LiTFSI-$Pyr_{14}TFSI$ solid polymer electrolyte exhibited good charge-discharge performance in Li/SPE/$LiFePO_4$ cells at $50^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• v.30 no.8
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• pp.1719-1723
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• 2009

The LiFeP$O_4$ powder was synthesized by using the solid state reaction method with Fe($C_2O_4){\cdot}2H_2O,\;(NH_4)_2HPO_4,\;Li_2CO_3$, and chitosan as a carbon precursor material for a cathode of a lithium-ion battery. The chitosan added LiFePO4 powder was calcined at 350 ${^{\circ}C}$ for 5 hours and then 800 ${^{\circ}C}$ for 12 hours for the calcination. Then we calcined again at 800 ${^{\circ}C}$ for 12 hours. We characterized the synthesized compounds via the crystallinity, the valence states of iron ions, and their shapes using TGA, XRD, SEM, TEM, and XPS. We found that the synthesized powders were carbon-coated using TEM images and the iron ion is substituted from 3+ to 2+ through XPS measurements. We observed voltage characteristics and initial charge-discharge characteristics according to the C rate in LiFeP$O_4$ batteries. The obtained initial specific capacity of the chitosan added LiFeP$O_4$ powder is 110 mAh/g, which is much larger than that of LiFeP$O_4$ only powder.

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

• Resources Recycling
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• v.31 no.4
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• pp.40-48
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• 2022

In waste lithium iron phosphate (LFP) batteries, the cathode material contains approximately 4% lithium. Recycling the constituent elements of batteries is important for resource circulation and for mitigating the environmental pollution. Li contained in the waste LFP cathode powder was selectively leached using persulfate-based oxidizing agents, such as sodium persulfate, potassium persulfate, and ammonium persulfate. Leaching efficiency and waste LFP powder properties were compared and analyzed. Pulp density was used as a variable during leaching, which was performed for 3 h under each condition. The leaching efficiency was calculated using the inductively coupled plasma (ICP) analysis of the leachate. All types of persulfate-based oxidizing agents used in this study showed a Li leaching efficiency over 92%. In particular, when leaching was performed using (NH₄)₂S₂O₈, the highest Li leaching percentage of 93.3% was observed, under the conditions of 50 g/L pulp density and an oxidizing agent concentration of 1.1 molar ratio.

• Proceedings of the Korean Magnestics Society Conference
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• 2007.12a
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• pp.208-209
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• 2007

• Proceedings of the Korean Magnestics Society Conference
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• 2015.11a
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• pp.99-99
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• 2015

• Clean Technology
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• v.30 no.1
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• pp.28-36
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• 2024

As demand for electric vehicles increases, the market for lithium-ion batteries is also rapidly increasing. The battery life of lithium-ion batteries is limited, so waste lithium-ion batteries are inevitably generated. Accordingly, lithium was selectively preleached from waste lithium iron phosphate (LiFePO₄, hereafter referred to as the LFP) cathode material powder among lithium ion batteries, and iron phosphate (FePO₄) powder was recovered. The recovered iron phosphate powder was mixed with alkaline sodium carbonate (Na₂CO₃) powder and heat treated to confirm its crystalline phase. The heat treatment temperature was set as a variable, and then the leaching rate and powder characteristics of each ingredient were compared after water leaching using Di-water. In this study, lithium showed a leaching rate of approximately 100%, and in the case of powder heat-treated at 800 ℃, phosphorus was leached by approximately 99%, and the leaching residue was confirmed to be a single crystal phase of Fe₂O₃. Therefore, in this study, lithium, phosphorus, and iron components were individually separated and recovered from waste LFP powder.