• Advances in materials Research
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• 제4권2호
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• pp.63-76
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• 2015

The energy crisis involving depletion of fossil fuel resource is not the sole driving force for developing renewable energy technologies. Another driving force is the ever increasing concerns on the air quality of our planet, associated with the continuous and dramatic increase of the concentration of greenhouse gas (mainly carbon dioxide) emissions. The internal combustion engine is a major source of distributed $CO_2$ emissions caused by combustion of gasoline derived largely from fossil fuel. Another major source of $CO_2$ is the combustion of fossil fuels to produce electricity. New technologies for generating electricity from sources that do not emit $CO_2$, such as water, solar, wind, and nuclear, together with the advent of plug-in hybrid electric vehicles (PHEV) and even all-electric vehicles (EVs), offer the potential of alleviating our present problem. Therefore, the relevant technologies in $LiFePO_4$ as cathode material for Li-ion batteries suitable to the friendly environment are reviewed aim to provide the vital information about the growing field for energies to minimize the potential environmental risks.

• Journal of Electrochemical Science and Technology
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• 제9권2호
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• pp.85-92
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• 2018

Olivine structure of $LiFePO_4$ (LFP) is one of the most commonly used materials in aqueous rechargeable lithium batteries (ARLBs), and can store and release charge through the insertion/de-insertion of $Li^+$ between LFP and FP. We have fabricated LFP and LFP/FP electrodes on titanium paper and studied their electrochemical properties in 2 M $Li_2SO_4$. The LFP/FP electrode was determined to be a suitable electrode for electo-ostmotic pump (EOP) in terms of efficiency in water and 0.5 mM $Li_2SO_4$ solution. Experiments to determine the effect of cations and anions on the performance of EOP using LFP/FP electrode have shown that $Li^+$ is the best cation and that the anion does not significantly affect the performance of the EOP. As the concentration of $Li_2SO_4$ solution was increased, the current increased. The flow rate peaked at $4.8{\mu}L/30s$ in 1.0 mM $Li_2SO_4$ solution and then decreased. When the EOP was tested continuously in 1.0 mM $Li_2SO_4$ solution, the EOP transported approximately 35 mL of fluid while maintaining a stable flow rate and current for 144 h.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.306-306
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• 2010

일반적으로 가장 많이 사용되고 있는 양극재료 가운데 $LiCoO_2$는 비교적 용량이 크고, 우수한 수명특성의 장점을 가지고 있는 반면, 단점으로 원재료의 높은 가격과 독성이 있으며, 열적으로 불안정하다. 반면, 원재료의 높은 가격과 독성, 열적 불안정성은 단점으로 지적된다. 이러한 단점을 극복할 수 있는 양극재료로 원료 가격이 저렴하고 높은 용량(170 mAh/g)과 열적으로 안정한 올리빈 구조를 형성하고 있는 $LiFePO_4$가 가장 이상적으로 고려되어져 왔다. 하지만 낮은 이온, 전기전도도 때문에 다양한 연구가 이루어졌다. 특성향상을 위한 연구가 필요하며, 다양한 전이금속의 도핑과 카본 코팅을 통하여 전기전도도의 향상과 함께 구조적으로도 리튬 이온의 확산을 더 용이하게 한다는 결과가 최근 보고되어 있다. 최근 다양한 전이금속의 도핑과 카본코팅을 통하여 전기전도도의 향상과 함께 구조적으로도 리튬이온의 확산을 더 용이하게 한다는 결과가 보고되어 있다. 본 연구에서는 고상반응법을 이용하여 $LiFePO_4$를 합성하였고, 카본소스를 첨가하여 전기전도도의 향상과 함께 높은 용량의 $LiFePO_4$/C양극재료를 합성하였다. 제조된 분말은 XRD 회절시험을 통하여 결정구조를 분석 하였으며, SEM을 이용하여 분말의 형상과 크기를 관찰 하였고, 또한 전기화학적 특성도 평가하였다.

• 한국수소및신에너지학회논문집
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• 제22권5호
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• pp.728-734
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• 2011

$LiFePO_4$ is a promising cathode material for secondary lithium batteries due to its high energy density, low cost and safety. $LiFePO_4$ was synthesized by the citrate process under reductive, neutral, and oxidative, atmospheres and the crystal structure was analyzed by X-ray powder diffraction. The samples synthesized under $N_2$ and $H_2$ atmosphere showed a single phase of a olivine structure, where the samples synthesized under $O_2$ atmosphere exhibited second phase of $Fe2O_3$. All the samples synthesized at 400, 600 and $800^{\circ}C$ under $N_2$ atmosphere presented a single phase of olivine. Residual organic material was observed for the sample synthesized at $400^{\circ}C$. There was nearly no intensity difference between the samples synthesized at $600^{\circ}C$ and $800^{\circ}C$. The electrochemical characteristic of the $LiFePO_4$ synthesized at $600^{\circ}C$ in the $N_2$ atmosphere was analyzed. The result exhibited an high discharge capacity of 160 mAh/g at the first cycle, and 155-160 mAh/g after 45 cycles.

• 전기화학회지
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• 제16권3호
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• pp.157-161
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• 2013

다공성 $LiMn_{0.6}Fe_{0.4}PO_4$ (LMFP)를 졸-겔법을 이용하여 합성하였고, 원료물질을 양론비로 혼합한 후 혼합물을 $600^{\circ}C$에서 10시간 동안 가열하여 입자 표면 전체에 전도성 탄소물질이 균일하게 형성된 LMFP을 제조하였다. LMFP의 결정구조는 리트펠트법에 의해 조사하였고, 표면구조와 기공특성은 주사전자현미경, 투과전자현미경, BET로 분석하였다. 제조된 LMFP는 표면적이 크고, 입자 표면에는 웹(web) 형태의 다공성 탄소층이 균일하게 형성되어 있는 것을 확인하였다. 상온에서 LMFP를 양극으로 사용하여 0.1 C의 전류밀도에서 초기방전용량은 152 mAh/g, 에너지밀도는 570 Wh/kg로 높았고 사이클 성능도 장기적으로 안정적이었다. 졸-겔법에 의해 제조된 LMFP는 높은 기공도와 균일한 탄소코팅에 의한 시너지효과로 이온확산이 용이하여 우수한 전기화학적 특성을 나타내었다.

• 전기화학회지
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• 제13권3호
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• pp.157-162
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• 2010

The electrodes comprising nano-sized $LiFePO_4$, carbon black and binder are prepared with two different Al current collectors. One is the generally used normal Al foil and the other is the chemically etched Al foil. Surface characteristics of each Al foil and electrochemical performance of the cathodes using each foil are investigated. The electrode from the etched Al foil exhibits better physical and electrochemical properties as compared to those of the normal Al foil because the etched Al foil has rough surface with sub-micron pores which improve the adhesion between the electrode materials and the substrate. The electrode on the etched Al foil has such a strong peel strength that the impedance is smaller than that of normal one. Indeed the $LiFePO_4$ electrode from the etched Al foil exhibits a better rate capability and remains intact even after storage for 1 week at the charged state at the elevated temperature $60^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• 제33권7호
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• pp.2315-2319
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• 2012

To improve the performance of $LiFePO_4F$, a novel sol-gel process is developed. For comparison, ceramic process is also implemented. From X-ray diffraction results we know that each sample adopts a triclinic $P{\bar{1}}$ space group, and they are isostructural with amblygonite and tavorite. The scanning electron microscope images show that the homogeneous grains with the dimension of 300-500 nm is obtained by the sol-gel process; meanwhile the sample particles obtained by ceramic process are as big as 1000-3000 nm. By galvanostatic tests and at electrochemical impedance spectroscopy method, the sample obtained by sol-gel process presents better electrochemical properties than the one obtained by ceramic process.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.350-351
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• 2007

The $LiFePO_4$ as cathode materials for lithium ion batteries was synthesized by the solid-state reaction using ballmiller and employed one step heat treatment at $650^{\circ}C$. The influence of the heating time on the structure, particle size and cycle performance was investigated. $LiFePO_4$ heated at $650^{\circ}C$ for 3 h exhibited higher discharge capacity of 140 mAh/g and excellent cycle performance.

• Journal of Electrical Engineering and Technology
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• 제11권6호
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• pp.1664-1673
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• 2016

Lithium rechargeable cells are used in many industrial applications, because they have high energy density and high power density. For an effective use of these lithium cells, it is essential to build a reliable battery management system (BMS). Therefore, the state of charge (SOC) estimation is one of the most important techniques used in the BMS. An appropriate modeling of the battery characteristics and an accurate algorithm to correct the modeling errors in accordance with the simplified model are required for practical SOC estimation. In order to implement these issues, this approach presents the comparative analysis of the SOC estimation performance using equivalent electrical circuit modeling (EECM) and noise suppression technique (NST) in three representative $LiCoO_2/LiFePO_4/LiNiMnCoO_2$ cells extensively applied in electric vehicles (EVs), hybrid electric vehicles (HEVs) and energy storage system (ESS) applications. Depending on the difference between some EECMs according to the number of RC-ladders and NST, the SOC estimation performances based on the extended Kalman filter (EKF) algorithm are compared. Additionally, in order to increase the accuracy of the EECM of the $LiFePO_4$ cell, a minor loop trajectory for proper OCV parameterization is applied to the SOC estimation for the comparison of the performances among the compared to SOC estimation performance.

• 한국재료학회지
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• 제34권4호
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• pp.185-193
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• 2024

In this study, NASICON-type Li_1+XGa_XTi_2-X(PO₄)₃ (x = 0.1, 0.3 and 0.4) solid-state electrolytes for all-solid-state batteries were synthesized through the sol-gel method. In addition, the influence on the ion conductivity of solid-state electrolytes when partially substituted for Ti⁴⁺ (0.61Å) site to Ga³⁺ (0.62Å) of trivalent cations was investigated. The obtained precursor was heat treated at 450 ℃, and a single crystalline phase of Li_1+XGa_XTi_2-X(PO₄)₃ systems was obtained at a calcination temperature above 650 ℃. Additionally, the calcinated powders were pelletized and sintered at temperatures from 800 ℃ to 1,000 ℃ at 100 ℃ intervals. The synthesized powder and sintered bodies of Li_1+XGa_XTi_2-X(PO₄)₃ were characterized using TG-DTA, XRD, XPS and FE-SEM. The ionic conduction properties as solid-state electrolytes were investigated by AC impedance. As a result, Li_1+XGa_XTi_2-X(PO₄)₃ was successfully produced in all cases. However, a GaPO₄ impurity was formed due to the high sintering temperatures and high Ga content. The crystallinity of Li_1+XGa_XTi_2-X(PO₄)₃ increased with the sintering temperature as evidenced by FE-SEM observations, which demonstrated that the edges of the larger cube-shaped grains become sharper with increases in the sintering temperature. In samples with high sintering temperatures at 1,000 ℃ and high Ga content above 0.3, coarsening of grains occurred. This resulted in the formation of many grain boundaries, leading to low sinterability. These two factors, the impurity and grain boundary, have an enormous impact on the properties of Li_1+XGa_XTi_2-X(PO₄)₃. The Li_1.3Ga_0.3Ti_1.7(PO₄)₃ pellet sintered at 900 ℃ was denser than those sintered at other conditions, showing the highest total ion conductivity of 7.66 × 10^-5 S/cm at room temperature. The total activation energy of Li-ion transport for the Li_1.3Ga_0.3Ti_1.7(PO₄)₃ solid-state electrolyte was estimated to be as low as 0.36 eV. Although the Li_1+XGa_XTi_2-X(PO₄)₃ sintered at 1,000 ℃ had a relatively high apparent density, it had less total ionic conductivity due to an increase in the grain-boundary resistance with coarse grains.