• Proceedings of the KIPE Conference
• /
• 2011.11a
• /
• pp.51-52
• /
• 2011

전류 적산법(Coulomb counting, Ampere counting)을 이용한 배터리 SOC(State of Charge) 추정 방식은 초기 SOC 값에 존재하는 오차와 SOC를 추정하는 시간동안 누적되는 전류값의 오차로 인해 추정이 실패할 수 있는 단점이 존재한다. 하지만 알고리즘이 직관적이며 단시간 내에서는 그 오차가 크지않고, 상용화된 배터리 SOC 추정 IC가 존재하여 구현이 간단하다는 장점 또한 있다. 본 논문에서는 전류 적산법 기반의 배터리 SOC 추정 IC를 사용하여 $LiFePO_4$ 리튬 폴리머 배터리의 SOC 추정 회로를 구현하는 과정을 제안한다. 또한 실험을 통해 제안된 배터리 SOC 추정 회로의 성능을 확인해본다.

• Journal of Power Electronics
• /
• v.18 no.5
• /
• pp.1585-1594
• /
• 2018

The estimation of $LiFePO_4$/graphite battery states suffers from the prominent hysteresis phenomenon between the respective open-circuit voltage curves towards charging and discharging. A lot of hysteresis models have been documented to investigate the hysteresis mechanism. This paper reviews and deeply interprets four non-electrochemical hysteresis models and some improvements. These models can be conveniently incorporated into commonly used equivalent circuit models to reproduce battery behaviors. Through simulation and experimental comparisons of voltage predictions and state-of-charge estimations, the pros and cons of these models are presented.

• Journal of the Korean Applied Science and Technology
• /
• v.28 no.3
• /
• pp.329-334
• /
• 2011

The electrochemical performances of an asymmetric hybrid capacitor were investigated using $LiFePO_4$ as the positive electrode and active carbon fibers(ACF) as the negative electrode. The electrochemical behaviors of a nonaqueous hybrid capacitor were characterized by constant current charge/discharge test. The specific capacitance using $LiFePO_4$/ACF electrode turned out to be $0.87F/cm^2$ and the unit cell showed excellent cycling performance. This hybrid capacitor was able to deliver a specific energy as high as 178 Wh/kg at a specific power of 1,068 W/kg.

• Proceedings of the KIPE Conference
• /
• 2017.07a
• /
• pp.463-464
• /
• 2017

다른 리튬계열 전지와 달리, 인산철($LiFePO_4$) 배터리는 중간 동작 영역에서 개방전압(OCV; open-circuit voltage)의 히스테리시스(hysteresis) 영역이 존재한다. 그러므로, 인산철 배터리 관리시스템, 특히 충전상태(SOC; state-of-charge)와 수명상태(SOH; state-of-health)의 정확한 모니터링을 위해서는 OCV의 정밀성이 요구된다. 본 논문에서는, 충전 및 방전 OCV-SOC의 SOC 간격에 따른 인산철 배터리의 SOH를 비교하기 위해 전기적 등가회로 모델(ECM; electrical-circuit modeling)적응제어 알고리즘 기반 실시간 내부저항(DCIR; direct current internal resistance)을 모니터링 하였다.

• Proceedings of the KIPE Conference
• /
• 2017.07a
• /
• pp.455-456
• /
• 2017

본 논문에서는 리튬 인산철 배터리($LiFePO_4$)의 내부 파라미터 추출 방법으로 전기화학적 기반인 정전류식 간헐적 적정 테크닉(galvanostatic intermittent titration technique;GITT)을 사용하였다. 배터리 관리 시스템(battery management system;BMS) 알고리즘의 기본적으로 들어가는 충방전 저항을 미세 구간으로 나누어 볼 수 있다. SOC(state-of-charge)에 맞는 저항 성분을 찾을 수 있고, 미소 용량 정보를 알아내어 특정 SOC 구간에서의 LFP 배터리 최적 운용 구간을 알 수 있다.

• Proceedings of the KIPE Conference
• /
• 2018.11a
• /
• pp.121-122
• /
• 2018

리튬 인산철(LFP, $LiFePo_4$) 배터리의 경우 다른 종류의 배터리에 비해 내부 파라미터가 비선형적인 단점이 있다. 일반적인 배터리 등가회로 모델을 적용 시, 비선형성으로 인해 추정 성능이 감소한다. 배터리 등가회로 모델을 기반인 확장 칼만 필터(EKF, Extended Kalman Filter)를 통해 SOC (State of Charge) 추정 시 추정성능이 감소할 수 있다. 따라서 본 논문은 LFP 배터리의 SOC 추정 성능 향상을 위해 실시간 파라미터 관측기를 통한 배터리 등가회로 모델을 기반으로 EKF의 내부 파라미터를 분석하고 이에 따른 차등 모델을 제안한다.

• Journal of Electrochemical Science and Technology
• /
• v.14 no.4
• /
• pp.320-325
• /
• 2023

In Li-ion batteries, a thick electrode is advantageous for lowering the inactive current collector portion and obtaining a high energy density. One of the critical failure mechanisms of thick electrodes is inhomogeneous lithiation and delithiation owing to the axial location of the electrode. In this study, it was confirmed that the top layer of the composite electrode contributes more to the charging step owing to the high ionic transport from the electrolyte. A high-loading multilayered electrode containing LiFePO₄ (LFP) and LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) was developed to overcome the inhomogeneous electrochemical reactions in the electrode. The electrode laminated with LFP on the top and NCM811 on the bottom showed superior cyclability compared to the electrode having the reverse stacking order or thoroughly mixed. This improvement is attributed to the structural and interfacial stability of LFP on top of the thick electrode in an electrochemically harsh environment.

• Clean Technology
• /
• v.29 no.2
• /
• pp.87-94
• /
• 2023

The recovery of valuable metals from waste lithium-based secondary batteries is very important in terms of efficiently utilizing earth's limited number of resources. Currently, the cathode material of a LiFePO₄ battery, a type of battery which is widely used in automobiles, contains approximately 5% lithium. After use, the lithium in these batteries can be used again as a raw material for new batteries through lithium recycling. In this study, low-concentration sulfuric acid, a commonly used type of inorganic acid, was used to selectively leach the lithium contained in a waste LiFePO₄ cathode material powder. In addition, in order to compare and analyze the leaching efficiency and separation efficiency of each component, the optimalleaching conditions were derived by applying a two-step leaching process with pulp density being used as a variable during leaching. When leaching with pulp density as a variable, it was confirmed that at a pulp density of 200 g/L, the separation efficiency was approximately 200 times higher than at other pulp densities because the iron and phosphorus components were hardly leached at this pulp density. Accordingly, the pulp density of 200 g/L was used tooptimize the leaching conditions for the selective leaching and recovery of lithium.

• Journal of the Korean Magnetic Resonance Society
• /
• v.18 no.2
• /
• pp.63-68
• /
• 2014

$^7Li$ nuclear magnetic resonance (NMR) spectra have been observed for $LiMPO_4$ (M = Fe, Mn) samples, as a promising cathode material of lithium ion battery. Observed $^7Li$ shifts of $LiFe_{1-x}Mn_xPO_4$ (x = 0, 0.6, 0.8, and 1) synthesized with solid-state reaction are compared with calculated $^7Li$ shift ranges based on the supertranferred hyperfine interaction of Li-O-M. Ex situ $^7Li$ NMR study of $LiFe_{0.4}Mn_{0.6}PO_4$ in different cut-off voltage for the first charge process is also performed to understand the relationship between $^7Li$ chemical shift and oxidation state of metals affected by delithiation process. The increment of oxidation state for metals makes to downfield shift of $^7Li$ by influencing the supertranferred hyperfine interaction.

• Journal of Electrochemical Science and Technology
• /
• v.13 no.4
• /
• pp.438-452
• /
• 2022

For cuboid and ellipsoid crystallites of LiFePO₄ powders, by X-ray diffraction (XRD) and microscopic (TEM) studies, it is possible to determine the anisotropic parameters of the crystallite size distribution functions. These parameters were used to describe the cathode rate capability within the model of averaging the diffusion coefficient D over the length of the crystallite columns along the [010] direction. A LiFePO₄ powder was chosen for testing the developed model, consisting of big cuboid and small ellipsoid crystallites (close to them). When analyzing the parts of big and small rate capabilities, the fitting values D = 2.1 and 0.3 nm²/s were obtained for cuboids and ellipsoids, respectively. When analyzing the results of cyclic voltammetry using the Randles-Sevcik equation and the total area of projections of electrode crystallites on their (010) plane, slightly different values were obtained, D = 0.9 ± 0.15 and 0.5 ± 0.15 nm²/s, respectively. We believe that these inconsistencies can be considered quite acceptable, since both methods of determining D have obvious sources of error. However, the developed method has a clearly lower systematic error due to the ability to actually take into account the shape and statistics of crystallites, and it is also useful for improving the accuracy of the Randles-Sevcik equation. It has also been demonstrated that the shape engineering of crystallites, among other tasks, can increase the cathode capacity by 15% by increasing their size correlation coefficients.