• Journal of Electrochemical Science and Technology
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• 제13권3호
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• pp.362-368
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• 2022

The application of polymer composite electrolyte in all-solid-state lithium-sulfur battery (ASSLSBs) can guarantee high energy density and improve the interface contact between electrolyte and electrode, which has a broader application prospect. However, the inherent insulation of the sulfur-cathode leads to a low electron/ion transfer rate. Carbon materials with high electronic conductivity and electrolyte materials with high ionic conductivity are usually selected to improve the electron/ion conduction of the composite cathode. In this work, PEO-LiTFSI-LLZO composite polymer electrolyte (CPE) with high ionic conductivity was prepared. The ionic conductivity was 1.16×10^-4 and 7.26×10^-4 S cm^-1 at 20 and 60℃, respectively. Meanwhile, the composite sulfur cathode was prepared with Sulfur, reduced graphene oxide and composite polymer electrolyte slurry (S-rGO-CPEs). In addition to improving the ion conductivity in the cathode, CPEs also replaces the role of binder. The influence of different contents of CPEs in the cathode material on the performance of the constructed battery was investigated. The results show that the electrochemical performance of the all-solid-state lithium-sulfur battery is the best when the content of the composite electrolyte in the cathode is 40%. Under the condition of 0.2C and 45℃, the charging and discharging capacity of the first cycle is 923 mAh g^-1, and the retention capacity is 653 mAh g^-1 after 50 cycles.

• 한국전기전자재료학회논문지
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• 제33권5호
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• pp.411-417
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• 2020

In this study, we introduce a Na β"-alumina composite thick film as a solid electrolyte, to reduce the resistance of electrolyte for a Na/S battery. An alumina/zirconia composite material was used to enhance the mechanical properties of the electrolyte. A solid electrolyte of about 40 ㎛ thick was successfully fabricated through the conversion and tape-casting methods. In order to investigate the effect of the surface treatment process of the solid electrolyte on the battery performance, the electrolyte was polished by dry and wet processes, respectively, and then the Na/S batteries were prepared for analyzing the battery characteristics. The battery with the dry process performed much better than the battery made with the wet process. As a result, the battery manufactured by the dry process showed excellent performance. Therefore, it is confirmed that the surface treatment process of the solid electrolyte has an important effect on the battery capacity and coulombic efficiency, as well as the interface reaction.

• 반도체디스플레이기술학회지
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• 제21권3호
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• pp.114-118
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• 2022

The stabilized all-solid-state battery structure indicate a fundamental alternative to the development of next-generation energy storage devices. Existing liquid electrolyte structures severely limit battery stability, creating safety concerns due to the growth of Li dendrites during rapid charge/discharge cycles. In this study, a low-dimensional graphene quantum dot layer structure was applied to demonstrate stable operating characteristics based on Li+ ion conductivity and excellent electrochemical performance. Transmission electron microscopy analysis was performed to elucidate the microstructure at the interface. The low-dimensional structure of GQD-based solid electrolytes has provided an important strategy for stable scalable solid-state lithium battery applications at room temperature. This study indicates that the low-dimensional carbon structure of Li-GQDs can be an effective approach for the stabilization of solid-state Li matrix architectures.

• 전기화학회지
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• 제22권3호
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• pp.87-103
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• 2019

현재 상용화되어 있는 리튬이온전지에 사용하고 있는 비수계 유기 전해액은 가연성, 부식성, 고휘발성, 열적 불안정성 등의 단점 때문에 더욱 안전하고 장수명을 보이는 고체 전해질로 대체하는 연구가 진행되고 있으며, 이것은 전기자동차 및 에너지저장 시스템과 같은 중대형 이차전지에도 효율적으로 활용될 수 있다. 다양한 형태의 고체 전해질 중에서 현재 고분자 매트릭스에 활성 무기 충진재가 포함되어 있는 복합 고체 전해질이 고이온전도도와 전극과의 탁월한 계면접촉을 이루는데 가장 유리한 것으로 알려졌다. 본 총설에서는 우선 고체 전해질의 종류와 연혁에 관해 간단히 소개하고, 고분자 및 무기 충진재 (불활성 및 활성)로 구성되는 고체 고분자 전해질 및 무기 고체 전해질의 기본적 물성 및 전기화학적 특성을 개괄한다. 또한 이 소재들의 형상을 기준으로 입자형 (0D), 섬유형 (1D), 평판형 (2D), 입체형 (3D)의 형식으로 구성된 복합고체 전해질과 이에 따른 전고체 전지의 전기화학적 특성을 논의한다. 특히 리튬금속 음전극을 사용하는 전고체 전지에 있어서 양전극-전해질 계면, 음전극-전해질 계면, 입자간 계면의 특성에 관해 소개하고, 마지막으로 현재까지 보고된 관련 총설들을 참조하여 복합 고체 전해질 기술의 현재 요구조건 및 미래 전망을 알아본다.

• Journal of Electrochemical Science and Technology
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• 제14권1호
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• pp.85-95
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• 2023

In recent years, solid-state Li metal batteries (SSLBs) have attracted significant attention as the next-generation batteries with high energy and power densities. However, uncontrolled dendrite growth and the resulting pulverization of Li during repeated plating/stripping processes must be addressed for practical applications. Herein, we report a plastic-crystal-based polymer/ceramic composite solid electrolyte (PCCE) to resolve these issues. To fabricate the one-side ceramic-incorporated PCCE (CI-PCCE) film, a mixed precursor solution comprising plastic-crystal-based polymer (succinonitrile, SN) with garnet-structured ceramic (Li₇La₃Zr₂O₁₂, LLZO) particles was infused into a thin cellulose membrane, which was used as a mechanical framework, and subsequently solidified by using UV-irradiation. The CI-PCCE exhibited good flexibility and a high room-temperature ionic conductivity of over 10^-3 S cm^-1. The Li symmetric cell assembled with CI-PCCE provided enhanced durability against Li dendrite penetration through the solid electrolyte (SE) layer than those with LLZO-free PCCEs and exhibited long-term cycling stability (over 200 h) for Li plating/stripping. The enhanced Li⁺ transference number and lower interfacial resistance of CI-PCCE indicate that the ceramic-polymer composite layer in contact with the Li anode enabled the uniform distribution of Li⁺ flux at the interface between the Li metal and CI-PCCE, thereby promoting uniform Li plating/stripping. Consequently, the Li//LiFePO₄ (LFP) full cell constructed with CI-PCCE demonstrated superior rate capability (~120 mAh g^-1 at 2 C) and stable cycle performance (80% after 100 cycles) than those with ceramic-free PCCE.

• 전기화학회지
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• 제21권4호
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• pp.80-87
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• 2018

웨어러블 디바이스, 전기자동차와 에너지저장시스템에 대한 전력 수요가 증가함에 따라 리튬이온 전지에 있어서 안전성은 가장 중요한 요소가 되었다. 이러한 문제를 해결하기 위해 가연성의 유기 액체전해질이 불연성의 고체전해질로 대체된 전고체 전지를 제조하려는 연구들이 진행되고 있다. 그러나 고체전해질은 자체 이온전도도가 상대적으로 낮고 전극/전해질 계면에서 높은 저항이 발생하므로 실질적인 활용에 제약이 있었다. 이에 유무기 소재로 구성된 복합전해질은 고체전해질의 단점을 극복할 수 있는 대안으로 떠오르고 있다. 본 연구에서는 PEO 전해질과 LLZO 고체전해질을 복합화하여 전해질을 제조하였고, LLZO 고체전해질 함량에 따라 결정성, 형상 및 전기화학 성능 분석을 진행하였다. 결과로부터 PEO 전해질 내에 LLZO 고체전해질의 최적 함량 및 균일한 분포가 전체 복합전해질의 이온전도도 향상에 중요한 요소임을 확인하였다.

• 한국재료학회지
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• 제29권2호
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• pp.121-128
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• 2019

Supercapacitors are attracting much attention in sensor, military and space applications due to their excellent thermal stability and non-explosion. The ionic liquid is more thermally stable than other electrolytes and can be used as a high temperature electrolyte, but it is not easy to realize a high temperature energy device because the separator shrinks at high temperature. Here, we report a study on electrochemical supercapacitors using a composite electrolyte film that does not require a separator. The composite electrolyte is composed of thermoplastic polyurethane, ionic liquid and fumed silica nanoparticles, and it acts as a separator as well as an electrolyte. The silica nanoparticles at the optimum mass concentration of 4wt% increase the ionic conductivity of the composite electrolyte and shows a low interfacial resistance. The 5 wt% polyurethane in the composite electrolyte exhibits excellent electrochemical properties. At $175^{\circ}C$, the capacitance of the supercapacitor using our free standing composite electrolyte is 220 F/g, which is 25 times higher than that at room temperature. This study has many potential applications in the electrolyte of next generation energy storage devices.

• Journal of Ceramic Processing Research
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• 제19권5호
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• pp.413-418
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• 2018

All-solid-state lithium batteries (ASSBs) using inorganic sulfide-based solid electrolytes are considered prospective alternatives to existing liquid electrolyte-based batteries owing to benefits such as non-flammability. However, it is difficult to form a favorable solid-solid interface among electrode constituents because all the constituents are solid particles. It is important to form an effective electron conduction network in composite cathode while increasing utilization of active materials and not blocking the lithium ion path, resulting in excellent cell performance. In this study, a mixture of fibrous VGCF and spherical nano-sized Super P was used to improve rate performance by fabricating valid conduction paths in composite cathodes. Then, composite cathodes of ASSBs containing 70% and 80% active materials ($LiNi_{0.6}Co_{0.2}Mn_{0.2}O_2$) were prepared by a solution-based process to achieve uniform dispersion of the electrode components in the slurry. We investigated the influence of binary carbon additives in the cathode of all-solid-state batteries to improve rate performance by constructing an effective electron conduction network.

• 한국세라믹학회지
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• 제48권1호
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• pp.110-115
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• 2011

$Gd_2O_3$-doped $CeO_2$ (GDC) and $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3$ (LSCF) composite cathode materials were prepared in order to be applied to intermediate-temperature solid oxide fuel cells. The electrochemical polarization was evaluated using ac impedance spectroscopy involving geometric restriction at the interface between an ionic electrolyte and a mixed-conducting cathode. In order to optimize the cathode composites applicable to a GDC electrolyte, the cathode composites were evaluated in terms of polarization losses with regard to a given electrolyte, i.e., GDC electrolyte. The polarization increased significantly with decreasing temperature and was critically dependent on the compositions of the composite cathodes. The optimized cathode composite was found to consist of GDC 50 wt% and LSCF 50 wt%; the corresponding normalized polarization loss was calculated to be 0.64 at $650^{\circ}C$.

• 전기화학회지
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• 제19권3호
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• pp.101-106
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• 2016

본 연구에서는 리튬 고분자 이차전지의 안정성과 전기화학적 특성을 향상시키기 위하여 poly(ethylen oxide)(PEO)를 lithium bis (trifluoromethanesulfonyl)imide, N-butyl-N-methylpyrrolidinium bis (trifluoromethanesulfonyl)imide 와 블렌딩-가교 법으로 복합화시켜 PEO-LiTFSI-$Pyr_{14}TFSI$ 고분자 전해질을 제조하였다. 전기화학적 산화 안정성 테스트에서 PEOLiTFSI-$Pyr_{14}TFSI$ 복합 고분자 전해질은 비록 4.4 V에서 약간의 산화곡선을 보이지만 5.7 V까지 안정하였다. PEO-LiTFSI-$Pyr_{14}TFSI$ 고분자 전해질은 온도가 증가할수록 이온전도도가 증가하며, PEO계열의 고분자 전해질의 특성상 상온에서 $10^{-6}S\;cm^{-1}$로 낮지만 $70^{\circ}C$에서는 $10^{-4}S\;cm^{-1}$까지 증가 하였다. 리튬 고분자 전지의 전기화학적 특성을 측정하기 위해 $LiFePO_4$ 양극, PEOLiTFSI-$Pyr_{14}TFSI$ 복합 고분자 전해질, 리튬 음극으로 전지를 구성하였으며 0.1 C의 전류밀도에서 방전 용량이 $30^{\circ}C$에서 $40mAh\;g^{-1}$, $40^{\circ}C$에서는 $69.8mAh\;g^{-1}$, $50^{\circ}C$에서는 $113mAhg^{-1}$을 나타내 온도의 증가에 따라 방전 용량이 증가함을 알 수 있었다. PEO-LiTFSI-$Pyr_{14}TFSI$ 복합 고분자 전해질은 $LiFePO_4$양극과 함께 50도에서 가장 우수한 충-방전 성능을 보여주었다.