• Carbon letters
• /
• 제1권3_4호
• /
• pp.148-153
• /
• 2001

The initial irreversible capacity, $Q_i$, is one of the parameters to express the material balancing of the cathode to anode. We introduced new terms, which are the initial intercalation Ah efficiency (IIE) and the initial irreversible specific capacity at the surface ($Q_{is}$), to express precisely the irreversibility of an electrode/electrolyte system. Two terms depended on kinds of active-materials and compositions of the electrode, but did not change with charging state. MPCF had the highest value of IIE and the lowest value of $Q_{is}$ in 1M $LiPE_6$/EC + DEC (1 : 1 volume ratio) electrolyte. IIE value of $LiCoO_2$ electrode was 97-98%, although the preparation condition of the material and the electrolyte were different. $Q_{is}$ value of $LiCoO_2$ was 0~1 mAh/g. MPCF-$LiCoO_2$ cell system had the lowest of the latent capacity. $Q_{is}$ value increased slightly by adding conductive material. IIE and $Q_{is}$ value varied with the electrolyte. By introducing PC to EC+DEC mixed solvent, IIE values were retained, but $Q_{is}$ increased. In case of addition of MP, IIE value increased and $Q_{is}$ value also increased a little.

• Journal of Electrochemical Science and Technology
• /
• 제7권3호
• /
• pp.228-233
• /
• 2016

It is hard to employ the carbon materials or the lithium metal foil for the anode of lithium sulfur batteries because of the poor passivation in ether-based electrolytes and the formation of lithium dendrites, respectively. Herein, we investigated the electrochemical characteristics of lithium sulfur batteries with lithiated silicon anode in the liquid electrolytes based on ether solvents. The silicon anodes were lithiated by direct contact with lithium foil in a 1M lithium bis(trifluoromethane sulfonyl) imide (LiTFSI) solution in 1,2-dimethoxyethane (DME) and 1,3-dioxolane (DOL) at a volume ratio of 1:1. They were readily lithiated up to ~40% of their theoretical capacity with a 30 min contact time. In particular, the carbon mesh reported in our previous work was employed in order to maximize the performance by capturing the dissolved polysulfide in sulfur cathode. The reversible specific capacity of the lithiated silicon-sulfur batteries with carbon mesh was 1,129 mAh/g during the first cycle, and was maintained at 297 mAh/g even after 50 cycles at 0.2 C, without any problems of poor passivation or lithium dendrite formation.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2005년도 추계학술대회 논문집 Vol.18
• /
• pp.350-351
• /
• 2005

The electrochemical behavior of Si-C material synthesized by heating the mixture of silicon and polyvinylidene fluoride (PVDF). Coin cells of the type 2025 were made using the synthesized material and the electrochemical studies were performed. Si-C/Li cells were made by using the developed Si-C material. Charge/discharge test was performed at 0.1C hour rate. Initial charge and discharge capacities at Si-C material derived from 20 wt.% of PVDF was found to be 1,830 and 526 mAh/g respectively. Initial charge/discharge characteristics of the electrode were analyzed. The level of reversible specific capacity was about 216 mAh/g at Si-C material derived from 20 wt.% of PVDF, IIE, intercalation efficiency at initial charge/discharge, was 68 %. Surface irreversible specific capacity was 31 mAh/g, and average specific resistance was 2.6 ohm*g.

• 한국표면공학회지
• /
• 제56권1호
• /
• pp.62-68
• /
• 2023

Silicon (Si) is considered as a promising substitute for the conventional graphite due to its high theoretical specific capacity (3579 mAh/g, Li₁₅Si₄) and proper working voltage (~0.3V vs Li⁺/Li). However, the large volume change of Si during (de)lithiation brings about severe degradation of battery performances, rendering it difficult to be applied in the practical battery directly. As a one feasible candidate of industrial Si anode, silicon monoxide (SiO_x) demonstrates great electrochemical stability with its specialized strategy, downsized Si nanocrystallites surrounded by Li⁺ inactive buffer phase (Li₂O and Li₄SiO₄). Nevertheless, SiO_x inherently has the initial irreversible capacity and poor electrical conductivity. To overcome those issues, conformal carbon coating has been performed on SiO_x utilizing ethylbenzene as the carbon precursor of chemical vapor deposition (CVD). Through various characterizations, it is confirmed that the carbon is homogeneously coated on the surface of SiO_x. Accordingly, the carbon-coated SiOx from CVD using ethylbenzene demonstrates 73% of the first cycle efficiency and great cycle life (88.1% capacity retention at 50th cycle). This work provides a promising synthetic route of the uniform and scalable carbon coating on Si anode for high-energy density.

• 한국세라믹학회지
• /
• 제53권3호
• /
• pp.376-380
• /
• 2016

A composite electrode made of iron oxide nanoparticles/multi-wall carbon nanotube (iNPs/M) delivers high specific capacity and cycle durability. At a rate of $200mAg^{-1}$, the electrode shows a high discharge capacity of ${\sim}664mAhg^{-1}$ after 100 cycles, which is ~ 70% of the theoretical capacity of $Fe_3O_4$. Carbon black, carbon nanotube, and graphene as anode materials have been explored to improve the electrical conductivity and cycle stability in Li ion batteries. Herein, iron oxide nanoparticles on acid treated MWCNTs as a conductive platform are combined to enhance the drawbacks of $Fe_3O_4$ such as low electrical conductivity and volume expansion during the alloying/dealloying process. Enhanced performance was achieved due to a synergistic effect between electrically 3D networks of conductive MWCNTs and the high Li ion storage ability of $Fe_3O_4$ nanoparticles (iNPs).

• Corrosion Science and Technology
• /
• 제21권6호
• /
• pp.445-453
• /
• 2022

SiO_x was prepared from a mixture of Si and SiO₂ via high-energy ball milling as a negative electrode material for Li-ion batteries. The molar ratio of Si to SiO₂ as precursors and the milling time were varied to identify the synthetic condition that could exhibit desirable anode performances. With an appropriate milling time, the material showed a unique microstructure in which amorphous Si nanoparticles were intimately embedded within the SiO₂ matrix. The interface between the Si and SiO₂ was composed of silicon suboxides with Si oxidation states from 0 to +4 as proven by X-ray photoelectron spectroscopy and electrochemical analysis. With the addition of a conductive carbon (Super P carbon black) as a coating material, the SiO_x/C manifested superior specific capacity to a commercial SiO_x/C composite without compromising its cycle-life performance. The simple mechanochemical method described in this study will shed light on cost-effective synthesis of high-capacity silicon oxides as promising anode materials.

• 공업화학
• /
• 제9권7호
• /
• pp.1059-1064
• /
• 1998

본 연구는 리튬이온 이차전지용 탄소전극을 개발하기 위하여 다양한 종류의 흑연과 MCMB6-28을 대상으로 이루어졌다. 이들의 층간거리는 $3.358{\sim}3.363{\AA}$, BET 비 표면적은 $2.95{\sim}26.15m^2/g$이었다. 이들의 전기화학적 특성은 층간거리가 크고 적절한 크기의 BET 비 표면적을 가질 때 리튬의 삽입과 탈삽입 거동이 우수하였다. 다양한 결정성계 탄소전극 활물질에 도전재로 KJ-Black을 0, 3, 5wt% 첨가하였을 때 도전제의 함량이 많을수록 전극과 전해질의 계면저항은 작아지나 3wt%를 첨가하였을 때 우수한 가역성을 보였다. 정전류 충 방전 시 인가되는 전류밀도를 증가시킴에 따라 탄소부극의 방전용량은 작아졌다.

• 청정기술
• /
• 제19권1호
• /
• pp.44-50
• /
• 2013

리튬이온전지에서 음극활물질의 저장용량을 증가시키기 위하여 주석산화물에 대한 연구가 많이 수행되고 있다. 주석산화물은 기존의 흑연 음극활물질보다 충방전 용량이 높다. 하지만 충방전이 진행되는 동안에 부피팽창률이 높아서 활물질이 파괴되는 현상이 나타나므로 과도한 비가역용량이 문제가 된다. 이를 해결하기 위하여 물리적 완충역할을 하는 물질이 첨가된 복합산화물을 제조하였다. $SnO_2-SiO_2$ 복합산화물을 솔-젤법을 이용하여 제조하였다. 10 vol% 프로필렌기체를 이용하여 탄소피복을 하여 전기전도성을 증가시켰다. TG/DTA, XRD, SEM과 FT-IR을 이용하여 제조된 물질의 물성을 분석하였으며, CR2032 코인셀을 제조하여 전기화학적인 특성을 조사하였다. $300^{\circ}C$로 열처리한 후에 탄소피복한 $SnO_2-SiO_2$ 활물질의 전기화학적 특성이 가장 우수하였다.

• Journal of Industrial and Engineering Chemistry
• /
• 제68권
• /
• pp.146-152
• /
• 2018

Due to their excellent mechanical durability and high electrical conductivity, carbon and silicon composites are potentially suitable anode materials for Li-ion batteries with high capacity and long lifespan. Nevertheless, the limitations of the composites include their poor ionic diffusion at high current densities during cycling, which leads to low ultrafast performance. In the present study, seeking to improve the ionic diffusion using hydrothermal method, electrospinning, and carbonization, we demonstrate the unique design of excavated carbon and silicon composites (EC/Si). The outstanding energy storage performance of EC/Si electrode provides a discharge specific capacity, impressive rate performance, and ultrafast cycling stability.

• Korean Chemical Engineering Research
• /
• 제57권5호
• /
• pp.672-678
• /
• 2019

리튬이차전지용 음극재로서 피치로 코팅된 천연흑연의 전기화학적 특성이 조사되었다. 천연흑연과 피치의 혼합물을 $1000^{\circ}C$에서 소성하여 음극재를 제조하였다. 다양한 연화점의 피치가 탄소전구체로 사용되었다. 제조된 음극재의 물리적 특성은 TGA, SEM, PSA 및 BET로 분석하였다. 피치의 연화점이 증가할수록 코팅 층의 두께가 증가하였고, 비표면적이 감소하였다. 초기 충 방전 효율, 사이클, 순환전압전류, 속도 특성 및 임피던스 테스트를 통해 전기화학적 성능을 조사하였다. 연화점 $250^{\circ}C$의 피치로 탄소 코팅된 천연흑연은 초기 방전용량 361 mAh/g과 쿨롱 효율 92.6%을 보였다. 또한 출력 특성(5 C/0.2 C)은 코팅되지 않은 천연흑연에 비해 1.6배 향상되었으며, 0.5 C로 진행된 사이클 테스트에서 50 사이클 후 90%의 용량 유지율을 나타내었다.