• 산업기술연구
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• 제43권1호
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• pp.43-48
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• 2023

Spinel LiNi_0.5Mn_1.5O₄ (LNMO) has been considered as one of most promising cathode material, because of its low-cost and competitive energy density. However, 4.7V vs. Li/Li⁺ of high operating potential facilitates electrolyte degradation on cathode-electrolyte interface during charge-discharge process. In particular, commercial polyvinylidene fluoride (PVDF) is not sutaible for LNMO cathode binder because its weak van der waals force induces thick and non-uniform coverage on the cathode surface. In this review, we study high performance binders for LNMO cathode, which forms uniform coating layer to prevent direct contact between electrolyte and LNMO particle as well as modifying high quality cathode electrolyte interphase, improved cell performace.

• Journal of Electrochemical Science and Technology
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• 제13권1호
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• pp.128-137
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• 2022

For this study, the sol gel method was used to synthesize the spinel LiNi_0.5Mn_1.5O₄ (LNMO) electrode material. Structural, morphological, electrochemical, and kinetic aspects of the LNMO have been characterized. The synthesized LNMO was indexed with the Fd3m cubic space group. The excellent capacity retention indicates that the spinel framework of LNMO has the ability to withstand high rate charge-discharge throughout long cycle tests. The Li diffusion coefficient (D_Li) changes non-monotonically across three orders of magnitude, from 10^-9 to 10^-12 cm² s^-1 determined from GITT method. The variation of D_Li seemed to be related to three oxidation reactions that happened throughout the charging process. A small dip in D_Li at the beginning stage of Li deintercalation is correlated with the oxidation of Mn³⁺ to Mn⁴⁺. While two pronounced D_Li minima at 4.7 V and 4.75 V are due to the oxidation of Ni²⁺/Ni³⁺ and Ni³⁺/Ni⁴⁺ respectively. The depletion of D_Li at the high voltage region is attributed to the occurrence of two successive phase transformation phenomena.

• 한국전기전자재료학회논문지
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• 제35권2호
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• pp.194-198
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• 2022

All-solid-state thin-film battery can realize the integration of electronic circuits into small devices. However, a high voltage cathode material is required to compensate for the low energy density. Therefore, it is necessary to study all-solid-state thin-film battery based on the high voltage cathode material LNMO. Nevertheless, the electrochemical properties deteriorate due to the problem of the interface between LiNi_0.5Mn_1.5O₄ (LNMO) and the solid electrolyte LiPON. In this study, to solve this problem, amorphous V₂O₅ was deposited as an interlayer between LNMO and LiPON. We confirmed the possibility of improving cycle performance of LNMO based thin-film battery. We expect that the results of this study can extend the battery lifespan of small devices using LNMO based all-solid-state thin-film battery.

• Journal of Electrochemical Science and Technology
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• 제8권1호
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• pp.53-60
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• 2017

Fluoroethylene carbonate (FEC) was studied as an additive for the electrolyte in lithium ion batteries with the $LiNi_{0.5}Mn_{1.5}O_4$ (LNMO) spinel cathode operating at a high potential beyond 4.7 V (vs. $Li/Li^+$). It was found that the FEC additive was electrochemically active for the $1^{st}$ charge cycle on the LNMO cathode. The presence of a large amount of FEC (more than 40 vol%) in the electrolyte caused severe side reactions with abnormally long voltage plateaus. In contrast, when the electrolyte contained less than 30 vol% FEC, the surface of the LNMO cathode was stabilized by the formation of the solid-electrolyte interphase (SEI), leading to improved cyclability. However, the resistance from the SEI limited the rate capability because of sluggish lithium transportation through the SEI and electronic insulation between the particles in the electrode.

• 전기화학회지
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• 제17권2호
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• pp.103-110
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• 2014

본 연구에서는 리튬 이차 전지의 가연성이 높은 액체 전해액의 대체 또는 개선을 위하여 이온성 액체 전해액으로 전극들에서의 거동을 관찰하였다. 이온성 액체인 1-ethyl-1-methyl piperidinium bis(trifluoromethanesulfonyl)imide(PP12 TFSI)는 녹는점이 $85^{\circ}C$이므로 상온에서 고체상이다. PP12 TFSI를 단독으로 전해액에 사용할 수 없으므로 리튬 이온 전지용 용매와 혼합하여 사용한다. PP12 TFSI를 50 wt.% 이상 사용하면 난연성이 아주 좋은 반면에 점도가 높아서 전해액 함침이 어렵다. 이온성 액체의 비율을 44 wt.%(이온성 액체:용매=1:1.25 wt.%)로 맞추고, 혼합한 용매는 EC/DEC(1/1 vol.%)이며, $LiPF_6$의 농도가 1.5 M이 되도록 전해액을 준비하여 연구하였다. 준비한 전해액은 자가소화시간 25초의 준수한 난연성을 가지고 있으며, 여러 종류의 전극에서도 우수한 수명 성능을 보여주었다. 적용된 전극은 $LiNi_{0.5}Mn_{1.5}O_4(LNMO)$, $LiFePO_4(LFP)$, $Li_4Ti_5O_{12}(LTO)$, artificial graphite이며, 특히 음극으로 사용된 artificial graphite에서의 전해액 분해를 방지하기 위한 첨가제의 거동도 관찰하였다. 여전히 전극으로의 함침의 문제가 다소 관찰이 되었으며 이런 문제가 개선될 수 있는 최적화된 혼합 이온성 액체 전해액이 개발된다면 이온성 액체의 난연성 특성은 더욱 활용성이 높아질 것이다.