Revisiting the conversion reaction in ultrafine SnO₂ nanoparticles for exceptionally high-capacity Li-ion battery anodes: The synergetic effect of graphene and copper

Kim, Da-Sol,Shim, Hyun-Woo,Dar, Mushtaq Ahmad,Yoon, Hyunseok,Song, Hee Jo,Kim, Dong-Wan Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.769 No.-

<P><B>Abstract</B></P> <P>Generally, in SnO<SUB>2</SUB>-based anode materials, the reversible alloying/dealloying reaction is the main Li-ion storage mechanism. Interestingly, these materials can show an exceptionally high capacity that is beyond the theoretical value (i.e., 783 mA h g<SUP>−1</SUP> based on Sn + 4.4Li<SUP>+</SUP> + 4.4e<SUP>−</SUP> ⇌ Li<SUB>4.4</SUB>Sn reaction), owing to the reversibility of the reaction between Sn and Li<SUB>2</SUB>O to form SnO<SUB>x</SUB> (x = 1, 2), so-called conversion reaction. Herein, we prepare Cu-reduced graphene oxide (rGO)-SnO<SUB>2</SUB> nanocomposites as a model system in order to demonstrate an effective strategy to improve the reversibility of the conversion reaction in SnO<SUB>2</SUB>. The incorporation of rGO can prevent the aggregation of SnO<SUB>2</SUB> nanoparticles. Furthermore, the Cu-rGO-SnO<SUB>2</SUB> nanocomposite exhibits the most improved conversion reaction reversibility, resulting in improved cycling performance and high capacity. Ex-situ transmission electron microscopy analysis confirms the high reversibility of the conversion as well as the alloying/dealloying reactions. Also, Cu nanoparticles promote the decomposition of amorphous Li<SUB>2</SUB>O, leading to enhancement of the conversion reaction between Sn and Li<SUB>2</SUB>O. Therefore, these results demonstrate a strategy for significantly improving the electrochemical performances of SnO<SUB>2</SUB>-based anodes for Li-ion batteries.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Cu-rGO-SnO<SUB>2</SUB> was prepared by hydrothermal and electrical wire explosion process. </LI> <LI> Well-dispersed SnO<SUB>2</SUB> NPs on rGO were more effective in the conversion reaction. </LI> <LI> Cu was used as a catalytic material to induce more reversible conversion reaction. </LI> <LI> SnO<SUB>x</SUB> in Cu-rGO-SnO<SUB>2</SUB> was reversibly formed by the conversion reaction. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Novel Heterogeneous Carbohydrase Reaction Systems for the Direct Conversion of Insoluble Carbohydrates : Reaction Characteristics and their Applications

Park, Dong Chan,Lee, Yong Hyun 한국미생물 · 생명공학회 1999 Journal of microbiology and biotechnology Vol.9 No.1

Most carbohydrates exist in nature in an insoluble state, which reduces their susceptibility towards various carbohydrases. Accordingly, they require intensive pretreatment for structural modification to enhance an enzyme reaction. The direct conversion of insoluble carbohydrates has distinct advantages for special types of reaction, especially exo-type carbohydrase; however, its application is limited due to structural constraints. This paper introduces two novel heterogeneous enzyme reaction systems for direct conversion of insoluble carbohydrates; one is an attrition coupled enzyme reaction system containing attrition-milling media for enhancing the enzyme reaction, and the other is a heterogeneous enzyme reaction system using extruded starch as an insoluble substrate. The direct conversion of typically insoluble carbohydrates, including cellulose, starch, and chitin with their corresponding carbohydrases, including cellulase, amylase, chitinase, and cyclodextrin glucanotransferase, was carried out using two proposed enzyme reaction systems. The conceptual features of the systems, their reaction characteristics and mechanism, and the industrial applications of the various carbohydrates are analyzed in this review.

바이오 디젤유 생산을 위한 대두유 에스테르화 반응의 속도론적 연구

황우람,신용섭 慶星大學校 環境問題硏究所 2002 環境硏報 Vol.12 No.1

The esterification of vegetable oil with methanol is one of the best ways to improve it's combustion characteristics. Therefore, in this study, the process which produce the bio-diesel oil from vegetable oil by the esterification reaction was investigated. Especially, the kinetic study on the esterification reaction of soybean oil was performed. Catalysts used in this study were sodium hydroxide as a homogeneous catalyst and calcium hydroxide as a heterogeneous catalyst. Because sodium hydroxide reacted with free fatty acid in the soybean oil and 0.5wt% of the sodium hydroxide was greater than the free fatty acid content in the soybean oil, it is very important for the completion of esterification reaction that the free fatty acid in the soybean oil should be removed before the esterification reaction. Compared with reaction rate constant of the esterification reaction rate constant of saponification had constant value in case of using sodium hydroxide catalyst. Interestingly, rate constant of the esterification reaction was decresed with increase of sodium hydroxide dosage. Compared with reaction rate constant of the esterification reaction, reaction rate constant of saponification had constant value in case of using sodium hydroxide catalyst. Interestingly, rate constant of the esterification reaction was decresed with increase of sodium hydroxide dosage. Using calcium hydroxide catalyste, reaction rate constants in FAMEs production step were Measured from 0.9141 min-1 to 1.0377 min-1, and reaction rate constants in monoglyceride and diglyceride production steps were measured from 0.0093 min-1 to 0.0386 min-1 according to the calcium hydroxide dosage. So, monoglyceride and diglyceride production steps rate controlling steps in overall esterification reaction.

계분을 이용한 탄화 반응속도에 대한 평가

김재경,이승희 한국폐기물자원순환학회 2015 한국폐기물자원순환학회지 Vol.32 No.6

Carbonization using chicken manure was used to obtain an energy source. In order to estimate the reaction rate at the optimal conditions for chicken manure in carbonization process it is estimated the reaction kinetics for the process. The carbonization process for chicken manure was optimized at carbonization temperature 300℃ to 400℃ in 20minutes. From the examination of conversion characteristics of chicken manure, carbonization reaction can be described by the 1st order kinetic reaction. Frequency factor(A) of reaction rate for chicken manure was evaluated to be 0.55 × 10−2 min−1 and the activation energy was estimated to be 3,815.0 kcal/kmol. As increased carbonization temperature from 250℃ to 400℃, reaction rate constant of chicken in the 1st order kinetic reaction is also increased from 0.0604 min−1 to 0.1383 min−1. In this study, carbonization degree of chicken manure in carbonization process was estimated by kinetic reaction deduction. The result of kinetic reaction in carbonization of chicken manure was evaluated to be 1st order kinetic reaction.

계분을 이용한 탄화 반응속도에 대한 평가

김재경,이승희 한국폐기물자원순환학회 2015 한국폐기물자원순환학회지 Vol.32 No.6

Carbonization using chicken manure was used to obtain an energy source. In order to estimate the reaction rate at theoptimal conditions for chicken manure in carbonization process it is estimated the reaction kinetics for the process. Thecarbonization process for chicken manure was optimized at carbonization temperature 300oC to 400oC in 20minutes. Fromthe examination of conversion characteristics of chicken manure, carbonization reaction can be described by the 1st orderkinetic reaction. Frequency factor(A) of reaction rate for chicken manure was evaluated to be 0.55×10−2min−1 and theactivation energy was estimated to be 3,815.0kcal/kmol. As increased carbonization temperature from 250oC to 400oC,reaction rate constant of chicken in the 1st order kinetic reaction is also increased from 0.0604min−1 to 0.1383min−1.In this study, carbonization degree of chicken manure in carbonization process was estimated by kinetic reaction deduction.The result of kinetic reaction in carbonization of chicken manure was evaluated to be 1st order kinetic reaction.

전환반응 기반 전이금속산화물 리튬이온전지 음극 활물질 개발 동향과 전망

권민재(Minjae Kwon),박종윤(Jongyoon Park),황종국(Jongkook Hwang) 한국세라믹학회 2022 세라미스트 Vol.25 No.2

The rapid increase in demand for high-performance lithium ion batteries (LIBs) has prompted the development of high capacity anode materials that can replace/complement the commercial graphite. Transition metal oxides (TMOs) have attracted great attention as high capacity anode materials because they can store multiple lithium ions (electrons) per unit formula via conversion reaction, resulting in high specific capacity (700-1,200 mAh g⁻¹) and volumetric capacity (4,000-5,500 mAh cm⁻³). In addition, TMOs are cheap, earth-abundant, non-toxic and environmentally friendly. However, there have been no reports of practical LIBs using conversion-based TMO anodes, because of several major problems such as large voltage hysteresis, low initial Coulombic efficiency (large initial capacity loss), low electrical conductivity, and large volume changes (100~200%). This review summarizes the recent progress, challenges and opportunities for TMO anode materials. The conversion reaction mechanism, problems and solutions of TMO anode materials are discussed. Considering iron oxide as a promising candidate, future research directions and prospects for the practical use of TMO for LIB are presented.

Conversion of methanol into light olefins over ZSM-11 catalyst in a circulating fluidized-bed unit

Xiaojing Meng,Huiwen Huang,Qiang Zhang,Minxiu Zhang,Chunyi Li,Qiukai Cui 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.3

Methanol conversion and the reaction pathway were investigated in a pilot-scale circulating fluidized-bed (CFB) unit over hierarchical ZSM-11 catalyst. Experimental results indicated that ZSM-11 catalyst was highly resistant to external coke due to the formation of mesopores. Elevated temperatures favored the production of propylene and butylene and decreased the yield of ethylene. Additionally, no direct relations were shown between the formation of ethylene and other products under different pressures, suggesting that ethylene was a primary product produced at the initial of the reaction. Methylation-cracking and oligomerization were verified as the main reaction pathway for the formation of C3 + alkenes., Methylation and oligomerization of olefins were dominated under high methanol partial pressure and consequently responsible for the production of higher olefins, while the b-scission of C7 = for propene and butylene, and C8 = for butylene were enhanced at low methanol partial pressure.

탄화공정을 통한 돈분의 반응속도 고찰

김재경,이민석,이승희 한국폐기물자원순환학회 2014 한국폐기물자원순환학회지 Vol.31 No.2

Carbonization process with pig manure is carried out to estimate the reaction kinetics with increasing carbonizationtime and temperature in the process. From the examination of conversion characteristics of pig manure, carbonizationreaction can be described by the 1st order kinetic reaction. Degree of carbonization, which can be expressed by C/H moleratio, is increased with increasing carbonization temperature. As increased carbonization temperature from 250oC to 400oC,reaction rate constant in the 1st order kinetic reaction is also increased from 0.0622min-1 to 0.1999min-1. Frequency factorand activation energy in Arrhenius equation for pig manure in the carbonization process can be decided by 1.06x10-3min-1 and 5441.8kcal/kmole, respectively. From the results of the reaction kinetics including TGA and SEM analysis,it is desirable that pig manure should be carbonized below carbonization temperature 400oC.

A surface-reactive high-modulus binder for the reversible conversion reaction of nanoparticular cobalt oxide

Lee, Myeong-Hee,Kim, Tae-Hee,Hwang, Chihyun,Kim, Jieun,Song, Hyun-Kon Pergamon Press 2017 Electrochimica Acta Vol. No.

<P><B>Abstract</B></P> <P>Conversion-reaction-based anode materials for lithium ion batteries (LIBs) such as transition metal oxides have been considered as high-capacity alternatives to graphite. In the conversion reactions, interestingly, microparticles have been known to be superior to nanoparticles in terms of capacity retention along repeated cycles. In this work, a cross-linked two-component binder system of poly(acrylic acid) and carboxymethyl cellulose (PAA/CMC) was used for nanoparticular Co<SUB>3</SUB>O<SUB>4</SUB>. The binder was characterized by high modulus and strong bonding to the surface oxide of Co<SUB>3</SUB>O<SUB>4</SUB>. Even without carbon coating, the composite electrodes of nanoparticular Co<SUB>3</SUB>O<SUB>4</SUB> in the presence of PAA/CMC showed significantly enhanced cycle retention with improved reversibility of the conversion reaction.</P>

Catalytic conversion of 1,1,1,2-tetrafluoroethane (HFC-134a)

한태욱,유범식,김영민,황병아,Gamal Luckman Sudibya,박영권,김승도 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.8

We examined the conversion of HFC-134a over five catalysts, Na2CO3, CaO, CaCO3, and two types of - Al2O3 with different surface areas, between 300 and 600 oC. HFC-134a was barely converted via the non-catalytic reaction, even at the highest temperature (600 oC). The operating temperatures for the catalytic conversion of HFC-134a were reduced dramatically and its efficiency increased with increasing temperature. Among the catalysts used, -Al2O3 with the larger surface area showed the highest conversion rate of HFC-134a, which was followed, in order, by -Al2O3 with the smaller surface area, CaCO3, CaO, and Na2CO3. The conversion rate of -Al2O3 decreased rapidly due to catalyst deactivation. The catalytic efficiency of -Al2O3 was maintained for a longer period by water addition. Water acted as a hydrogen donor for the dehydrofluorination reaction.