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This paper proposes low-melting-point eutectic salts containing RbCl as electrolytes for light weight thermal batteries. The handleability of the eutectic salts was remarkably improved for commercialisation. Their performance as thermal battery molten-salt electrolytes was verified using tests on a single cell and a 12-cell stacked battery.

High-energy-density rechargeable batteries have been gaining considerable importance in the field of renewable energy, and Li-infused anodes are potential candidates for the development of such batteries. However, the poor cycling and dimensional stability of Li affects their performance. As most materials used in battery manufacturing are lithiophobic to molten Li, infusion of Li into the porous structures with an intrinsically lithiophobic surface presents challenges in the development of Li batteries. Optimising and improving the wettability of molten Li is one approach to address this. Herein, we propose a very practical and straightforward oxidation method for achieving an ultra-lithiophilic NiO layer on the surface of a three-dimensional Ni-foam. Oxidation of the Ni-foam in air resulted in a remarkable increase in the wettability of molten Li on the Ni surface, with a decrease in the wetting angle from 120° to 0°. A NiO layer was epitaxially grown on the surface of the Ni-foam, with a thickness of several hundreds of nanometres. This layer was lithiophilic and showed high electrical conductivity. An anode prepared using Li-infused oxidised Ni-foam showed no evidence of short circuits or dendrite formation after 1000 cycles of stripping and plating at 0.1 and 0.5 mA cm−2, whereas a pure Li anode showed unstable stripping and plating behaviour at 0.5 mA cm−2. The proposed surface-treatment method is considered the most simple and practical method among those reported to date, and the Ni-foam produced using this method showed excellent anode performance. Hence, the proposed method will facilitate further development of rechargeable lithium-metal battery technology.

Numerous studies have addressed the commercial viability of lithium–air batteries (LABs). However, the high reactivity of Li with air moisture and CO2 has hindered the broad applicability of LABs. In this study, lithium-protective hybrid lithium–air batteries (HLABs) were fabricated with Super P (SP) and composites of fluorinated carbon (CFx), MoS2, and WS2 as the cathodes. Subsequently, their potential use as a power source for the next generation of defense technologies was investigated. It was observed that a single cell HLAB with the SP-CFx composite cathode exhibited a specific capacity of 893 mAhg−1cathode. In comparison, a Tomcell with the SP cathode demonstrated a specific capacity of 465 mAhg−1cathode when discharged. The cells with SP-MoS2 and SP-WS2 cathode yielded specific capacities of 357 and 386 mAhg−1cathode, respectively. The improved performance of the SP-CFx cell can be attributed to synergistic effects of lithium–air cell and lithium battery reactions between CFx and SP. To assess all functionalities of the SP-CFx HLAB, lithium-protective HLABs were fabricated and discharged in air. To operate the lithium–air battery in air, pure lithium metal was sealed with solid electrodes (lithium-ion conducting glass–ceramics (LICGC)) and a buffer electrolyte (1 M LiFTSI in TEGDME) was applied. The SP-CFx cell was discharged for 25 days in air, greatly exceeding the 72 h requirement for the next-generation soldier power systems. These results demonstrate significant potential for HLABs to be used as a pioneering power source in next-generation energy-independent tactical defense units.

Although numerous cathode materials with excellent properties have been developed for use in molten salt thermal batteries, similar progress is yet to be made with anode materials. Herein, a high-performance lithium-impregnated metal foam anode (LIMFA) is fabricated by impregnating molten lithium into a gold-coated iron–chrome–aluminum (FeCrAl) foam at 400°C. A test cell employing the LIMFA FeCrAl anode exhibited a specific capacity of 2,627 As·g−1. For comparison, a cell with a conventional Li(Si) anode was also discharged, demonstrating a specific capacity of 982 As·g−1. This significant improvement in performance can be attributed to the large amount (18 wt.%) of lithium incorporated into the FeCrAl foam and the ability of the FeCrAl foam to absorb and immobilize molten lithium without adopting a cup system. For thermal batteries without a cup, the LIMFA FeCrAl provides the highest-reported specific capacity and a flat discharge voltage curve of molten lithium. After cell discharge, the FeCrAl foam exhibited no lithium leakage, surface damage, or structural collapse. Given these advantageous properties, in addition to its high specific capacity, LIMFA FeCrAl is expected to aid the development of thermal batteries with enhanced performance.

The lithium(Li) primary batteries have been widely used in power sources for military applications. According to the military standards, the design temperatures for the basic climate category including the mid-altitude areas will include the ambient air temperature range of -32oC through +60oC, considering the operational, storage, and transit conditions of materiel systems. Among a variety of Li primary batteries, lithium/thionyl chloride (Li/SOCl2) primary batteries have been commonly utilized in military applications due to their high energy density, high operating voltage, and competitive cost. However, Li/SOCl2 batteries have serious challenges due to initial voltage delay by lithium chloride passivation layer and possible safety issues by a formation of toxic sulfur-dioxide (SO2) gas and solid sulfur during discharge. To overcome the intrinsic disadvantages of Li/SOCl2 batteries, research into lithium/carbon fluoride-manganese dioxide (Li/CFx-MnO2) batteries has been ramped up for military applications due to their high energy density and good rate capability. In this study, we have focused on an optimization of solvents and Li salts to improve the electrochemical performances of Li/CFx-MnO2 batteries in a wide operating temperature ranges. We have investigated candidate solvents for Li/CFx-MnO2 batteries with different compositions of methyl butyrate (MB) and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) as well as conventional solvents including propylene carbonate (PC), 1,2-dimethoxyethane (DME), tetrahydrofuran (THF), ethyl acetate (EA), and 1,2-dioxolane (DOL). Moreover, we have investigated the effects of Li salts, lithium perchlorate (LiClO4) and lithium bis(trifluoromethanesulfonyl)imide (LiFSI), on the electrochemical performances in the low and high operating temperatures. Ionic conductivity measurements and differential scanning calorimetry (DSC) analysis were also carried out to investigate the physical properties and stability of electrolyte. This study will provide an opportunity to develop the new electrolyte systems for Li/CFx-MnO2 batteries in a wide operating temperature window.

Lithium/Carbon fluoride (Li/CFx) primary batteries have been used in commercial applications, for example implantable cardiac pacemakers, due to their high energy density, long shelf life, and wide operation temperature range (-40oC to 85oC). However, the low electrical conductivity of CFx leads to a serious initial voltage delay at the beginning of discharge and the low rate capability of Li/CFx primary batteries. To overcome these issues, CFx materials are mixed with manganese dioxide (MnO2) to form hybrid cathodes due to a good rate capability of MnO2. Generally, the electrolytic manganese dioxide (EMD) used as cathode materials in Li/MnO2 primary batteries contains about 5% of water before heat treatment. The pristine EMD materials were heat-treated to reduce the water contents. However, water can be reabsorbed by cathode materials during processing and cathode formation. In this study, we investigated the effects of residual water contents in the pristine heat-treated EMD materials and as-fabricated CFx-MnO2 cathode electrodes on the self-discharge characteristics in Li/CFx-MnO2 primary batteries. Moreover, we investigated the effect of protective film on Li anode surface on the self-discharge characteristics in Li/CFx-MnO2 primary batteries. A protective film on Li anode surface was formed by immersing it in the electrolyte or carbon dioxide treatment. We believe that this study will provide useful guidance in the enhanced electrochemical properties and fabrication process of Li/CFx-MnO2 primary batteries.

Hydrothermally synthesized homogeneous structures based on Ni, Mo, and S on Ni metal foam cathodes (NiMoSs) were characterized electrochemically. A NiMoS-containing cell exhibited a much higher specific capacity of 1534 A s g-1 than an FeS2 cathode, owing to its homogeneous structure, demonstrating promise for thermal battery applications.

The oxygen electrode is the most critical component in lithium-air batteries for oxygen reduction and evolution reaction (ORR/OER) in order to get closer to the theoretical energy density of 11,238 Wh/kg, which is the best among the batteries ever developed. Many carbon materials have been researched as a candidate oxygen electrode for lithium-air batteries such as a carbon black, CNTs, and graphene. Compared to the many research results, there are still many controversies on the optimum oxygen electrode for lithium-air batteries. Besides that, carbon and binder have been known to deteriorate OER/ORR properties for lithium-air batteries by generating Li2CO3 and other bi-product. Recently, HER and OER properties of heterogeneous MoS2/Ni3S2 have been reported for water splitting. The heterogeneous HER and OER performances of MoS2/Ni3S2 were better than the commercial HER and OER catalysts. Up till now, to my best knowledge, there is no report on ORR properties for homogeneous NiMoS. Therefore, in order to research the ORR properties of homogeneous NiMoS, the homogeneous NiMoS has been synthesized on Ni-foam and Ni-powder by various solvothermal methods such as applying stirring during solvothermal synthesis, increasing the pressure or applying the both. Finally, we successfully synthesized NiMoS massively with stirring at the pressure of 15 bar. Characterization for NiMoSs variously synthesized were conducted with SEM, TEM as well as OER/ORR properties using RRDE (Ring Rotating Disk Electrode). As a result, homogeneous NiMoSs massively synthesized with stirring as well as high pressure of over 15 bar shows a unique homogeneous structure with sub-micron size. However, NiMoS synthesized under 2~3 bar pressure with no stirring shows the tens of micron size as well as heterogeneous structure. Intriguingly, OER/ORR properties of massively synthesized NiMoS shows much better OER/ORR properties compared to the solvothermally synthesized NiMoS with no-stirring and 2~3 bar pressure. These results show a very positive result for non-precious electrode material for next-generation Li-air battery as well as fuel cell field.

Lithium oxygen(Li-O2) batteries have been recognized as one of the next-generation power sources, capable of supplying power for a long time even in an independent extreme environment. In spite of the theoretical advantage, Li-O2 batteries face technical and economical challenges that must be addressed to promote them as commercially variable techcologies for future energy system. Above all, battery performance largely depends on the activities of the cathode during discharge and charge, respectively. The undesirable overpotential caused by sluggish reaction kinetics assiciated with the ORR and OER greatly limit the current performance of Li-O2 batteries, which must be improved by efficient catalyzing the reactions. Among the numerous catalysts, perovskite oxides have attention for candidate electrocatalyst for Li-O2 batteries due to their high electronic/ionic conductivity, high electrochemical stability, and catalytic activity. Especially, La0.6Sr0.4Co0.2Fe0.8O3(LSCF) is considered as a typical catalyst for Li-O2 batteries, which and provide high oxygen surface exchange coefficient for fast kinetics at the gas/electrode interface. The surface area is significantly related on the ORR and OER performance, which influences on the active area for reactions. In this study, we have tried to utilize a simple high energy ball milling process to investigate the electrochemical properties of LSCF catalyst. Through the BET analysis, it was confirmed that the specific area significantly was increased after ball milling due to the reduced particle size, obtaining the optimized milling time with the higher ORR performance. The electrochemical activities have been measured with rotating disk electrode(RRDE) method. Well-ball milled LSCF catalyst has resulted in the enlargement of specific surface area and increased defective sites, which improve the catalytic activity. To investigate the influence of LSCF oxides on the ORR process, the performance of composite electrode with LSCF catalyst in LITFSI in either solvents has been compared with a carbon based cathode(carbon nano tube(CM130)). From the discharge results, the composite electrode showed the superior performance as well as higher specific capacitance (more than 1.6 times) than carbon based electrode dye to the altered transport and reaction kinetics due to LSCF. In this study, we have proposed the processes of obtaining a catalyst with optimal electrochemical properties through a relatively simple process and applied it to electrode for lithium oxygen batteries.

High-power, large-capacity reserve thermal batteries are useful power sources for the actuators of guided weapons and propulsion for the underwater vehicles. However, unexpected thermal runaway and explosions can occur due to the thermal design error. Preventing such accidents is crucial and arduous challenge in developing high capacity, reliable thermal batteries. To do so, the heat balance between the heat source and the electrode/solid-electrolyte components must be carefully considered when designing a thermal battery. Herein, the optimal discharge temperatures and heat balances of thermal batteries are obtained through the discharge experiment of unit cells with Li(Si) and pure-Li anodes (LAN): (Li(Si): 500 °C/100 cal g⁻1, LAN: 550 °C/110 cal g⁻1). The thermal properties of two types of thermal batteries (150 V, 80 cells, 1 kWh) with Li(Si) and LAN are also analyzed using COMSOL Multiphysics software. Furthermore, to compare the performance, two high-power, large-capacity thermal batteries with the same heat-source energy (110 cal g⁻1) are fabricated and discharged at 40 A over 600 s. The experimentally evaluated temperatures of the cathodes, electrolytes, heat sources, and other components are found to be consistent with the simulation results suggesting that this study provides a complete and accurate computational methods to design high capacity thermal batteries.

The oxygen electrode is the most important component in lithium-air batteries for oxygen reduction and evolution reaction (OER/ORR) to get closer to the theoretical energy density of 11,238 Wh/kg, which is the best among the batteries ever developed. Many carbon materials have been researched as a candidate oxygen electrode for lithium-air batteries such as a carbon black, CNTs and graphene. Compared to the many research results, there are still many controversies on the optimum oxygen electrode for lithium-air batteries. Besides that, carbon and binder have been known to deteriorate OER/ORR properties for lithium-air batteries by generating Li2CO3 and other bi-product. Recently, HER and OER properties of heterogeneous MoS2/Ni3S2 have been reported for water splitting. The heterogeneous HER and OER performances of MoS2/Ni3S2 were better than the commercial HER and OER catalysts. Up till now, to my best knowledge, there's no report on ORR properties for homogeneous NiMoS. Therefore, to investigate the ORR properties of homogeneous NiMoS, the homogeneous NiMoS has been synthesized on Ni-foam as well as Ni-powder by various solvothermal methods such as applying to stir during solvothermal synthesis, increasing the pressure or applying the both. Finally, we successfully synthesized NiMoS massively with stirring at the pressure of 15 bar. Characterization for NiMOSs variously synthesized were conducted with SEM, TEM as well as OER/ORR properties using RRDE (Ring Rotating Disk Electrode). As a result, homogeneous NiMoSs massively synthesized with stirring as well as high pressure of over 15 bar shows a unique homogeneous structure with sub-micron size. However, NiMoS synthesized under 2~3bar pressure with no stirring shows the tens of micron size as well as heterogeneous structure. Intriguingly, OER/ORR properties of massively synthesized NiMoS shows much better OER/ORR properties compared to the solvothermal synthesized NiMoS with no-stirring and at the pressure of 2~3 bar. These results show a very optimistic result for non-precious electrode material for the next generation Li-air battery as well as the fuel cell field.

Nanotextured CuBi2O4 photocathodes have been developed for applications toward solar water splitting. Tailoring the CuBi2O4 photocathodes to yield a high photocurrent and a positively large onset potential demonstrates their applicability in a photoelectrochemical tandem cell for entirely solar-driven overall water splitting.

Micro/meso-porous reduced graphite oxide (MMRGO) nanosheets were produced using precursor carbide-derived carbon (CDC), which was produced at a high temperature of 1200 °C, through a massive wet chemistry synthetic route involving graphite oxidation and microwave reduction. X-ray diffraction (XRD) and transmission electron microscopy (TEM) show that the MMRGO nanosheets were fabricated with 2–3 layers and ripple-like corrugations. N2 sorption isotherms confirmed that micro/meso-pores coexisted in the RGO sample from CDC. In the anode application of Li-ion batteries, this RGO sample had an enhanced capacity performance at the 0.1 C rate and 1 C rate, with ∼1200 mAh g−1 at the 100th cycle and ∼1000 mAh g−1 at the 200th cycle, respectively.

Effect of the addition of conductive carbonaceous materials to the FeS2 (pyrite) cathode on electrochemical performance of thermal battery is investigated by adding carbon blacks (CBs) or multi-walled carbon nanotubes (MWCNTs) which has conductive network structures with various amounts from 0.1 to 1 wt.%, compared to the amount of pure FeS2. Among the samples prepared with various amounts of CB or MWCNT addition, the 1 wt.% CB-added sample exhibits the highest electrochemical properties. These results suggest that the improvement in the electrochemical performance of thermal batteries can be achieved by the addition of the conductive carbonaceous materials to pyrite electrode.

In this study, effects of pyrite () particle sizes on the electrochemical characteristics of thermal batteries are investigated using unit cells made of pulverized pyrite by ball-milling. At unit cell discharge test, the electrochemical capacity of pyrite-cell largely increases compared to pyrite-cell, and their internal resistances also decrease. These results are attributed to the increase in the active reaction area of pyrite by ball milling. However, at unit cell discharge test, a pyrite cell shows lower internal resistance than that of pyrite cell only at Z-phase region (). After that, a pyrite cell shows a decrease in the cell voltage and an rapid increase of the internal resistance in J-phase region () is observed compared to those of pyrite cell. It can be concluded that at the higher temperature, the thermally unstable pulverized pyrite is decomposed thermally as well as self discharged, simultaneously, which causes the higher resistance and lower capacity at in J-phase than that of pyrite cell.

Microstructure and thermal stability of mechanically ball milled were investigated. The average particle size and distribution of powder were changed in two steps with the increased ball milling time. The average particle size drastically decreased from to 1.01 and after ball milling of 10 h and 30 h, respectively. However, the distribution was broad and a shoulder appeared at because the pulverization was still in process at 10 h ball milling. After 60 h ball milling, the distribution became narrower. After ball milling of 120 h, the average particle size increased because of particle agglomeration. Therefore, the particle size distribution became broaden again. Finally, after ball milling of 170 h, with the narrowest size distribution can be obtained. Thermal stability of was unstable as the particle was pulverized. Therefore, the activation energy of the fine size particles is 27% lower than that of the as-received .

Lithium-impregnated metal foam anodes (LIMFAs) are fabricated and investigated. The LIMFAs are prepared by the impregnation of lithium into molten-salt-coated nickel metal foam. A single cell with the LIMFA exhibits a specific capacity of 3009 As g−1. For comparison, a single cell with a LiSi alloy anode is also discharged, demonstrating a specific capacity of 1050 As g−1. These significant improvements can be attributed to the large amount of lithium impregnated into the metal foam as well as the molten lithium holding capability of the foam. Due to their excellent electrochemical properties, LIMFAs are suitable for use in thermal batteries.

4 Agency for defense development, chochiwongil 462, Yuseong-Ku, Daejeon 305-152, Korea Abstract >> A proper stacking force and assembly are important to the performance of fuel cell. Improper assembly pressure may lead to leakage of fuels and high interfacial contact resistance, excessive assembly pressure may result in damage to the gas diffusion layer and other components. The pressure distribution of gas diffusion layer is important to make interfacial contact resistance less for stack performance. To analyze the influence of design parameter factors for pressure distribution, and to optimize stack design, DOE (Design of Experiment) was used for polymer electrolyte membrane fuel cell stack pressure test. As commonly known, the higher clamping force improves the fuel cell stack performance. However, non-uniformity of stress distribution is also increased. It shows that optimization between clamping force and stress distribution is needed for well designed structure of fuel cell stack. In this study, stack design optimization method is suggested by using FEM (Finite Element Methode) and DOE for light-weighted fuel cell stack.

3 Agency for defense development, chochiwongil 462, Yuseong-Ku, Daejeon 305-152, Korea Abstract >> In this paper, the development and performance analysis of a fuel cell-powered unmanned aerial vehicle is described. A fuel cell system featuring 1 kW proton exchange membrane fuel cell combined with a highly pressurized fuel supply system is proposed. For the higher fuel consumption efficiency and simplification of overall system, dead-end type operation is chosen and each individual system such as purge system, fuel supply system, cooling system is developed. Considering that fluctuation of exterior load makes it hard to stabilize fuel cell performance, the power management system is designed using a fuel cell and lithium-ion battery hybrid system. After integration of individual system, the performance of unmanned aerial vehicle is analyzed using data from flight and laboratory test. In the result, overall system was properly operated but for more duration of flight, research on weight lighting and improvement of fuel efficiency is needed to be progressed.

Thermal batteries have excellent mechanical robustness, reliability, and long shelf life. Due to these characteristics as well as their unique activation mechanism, thermal batteries are widely adopted as military power sources. Li(Si)/ thermal batteries, which are used mostly in these days, use LiCl-KCl and LiBr-LiCl-LiF as molten salt electrolyte. However, it is known that Li(Si)/ thermal batteries have high internal resistance. Especially, cathode accounts for the greater part of internal resistance in unit cell. Many efforts have been put into to decrease the internal resistance of thermal batteries, which result in the development of new electrode material and new electrode manufacturing processes. But the applications of these new materials and processes are in some cases very expensive and need complicated additional processes. In this study, internal resistance study was conducted by adding carbon black and carbon nano-tube, which has high electron conductivity, into the cathode. As a results, it was found that the decrease of internal resistance of cathode by the addition of carbon black and carbon nano-tube.

The dynamic mechanical thermal properties of carbon fiber-reinforced bismaleimide (BMI) composites processed using polyacrylonitrile(PAN)-based carbon fibers unsized and sized with LaRC PETI-5 amic acid oligomer as interphase material at 150°C, 250°C, and 350°C were investigated by means of dynamic mechanical thermal analysis. It was found that the storage modulus, loss modulus, tan δ and the peak temperature significantly depend on the sizing temperature as well as on the presence and absence of LaRC PETI-5 sizing interphase. The result showed that the carbon fiber/BMI composite sized at 150°C had the highest storage modulus at a measuring temperature of 250°C. The storage modulus decreased with increasing sizing temperature from 150°C to 350°C, being influenced by interdiffusion and co-reaction between the LaRC PETI-5 interphase and the BMI matrix resin. The present result is quite consistent with the interfacial result reported earlier in term of interfacial shear strength and interlaminar shear streng...

In the present paper, a variety of fiber reinforcements, for instance, stabilized OXI-PAN fibers, quasi-carbon fibers, commercial carbon fibers, and their woven fabric forms, have been utilized to fabricate pseudo-unidirectional (pseudo-UD) and 2-directional (2D) phenolic matrix composites using a compression molding method. Prior to fabricating quasi-carbon fiber/phenolic (QC/P) composites, stabilized OXI-PAN fibers and fabrics were heat-treated under low temperature carbonization processes to prepare quasi-carbon fibers and fabrics. The thermal conductivity and thermal expansion/contraction behavior of QC/P composites have been investigated and compared with those of carbon fiber/phenolic (C/P) and stabilized fiber/phenolic composites. Also, the chemical compositions of the fibers used have been characterized. The results suggest that use of proper quasi-carbonization process may control effectively not only the chemical compositions of resulting quasi-carbon fibers but also the thermal conductivity and thermal expansion behavior of quasi-carbon fibers/phenolic composites in the intermediate range between stabilized PAN fiber- and carbon fiber-reinforced phenolic composites.

A phenylethynyl-terminated imide oligomer (LaRC PETI-5®) with a number average molecular weight of 2500 g/mol has been applied onto the surfaces of PAN-based carbon fiber tows and woven carbon fabrics as a sizing material to introduce an interphase between the fiber and matrix in carbon/BMI composites. The adhesion between the fiber and matrix was enhanced by the presence of a properly processed LaRC PETI-5® interphase. The results showed that when LaRC PETI-5® was sized and processed at 150°C, the interfacial shear strength (IFSS) of unidirectional IM7/BMI composite measured by using a microindentation technique and the interlaminar shear strength (ILSS) of a carbon/BMI composite measured by short beam shear test were markedly improved by about 35% and 66%, respectively, in comparison with the unsized counterparts. The adhesion enhancement strongly depends not only on the presence or absence of LaRC PETI-5® sizing interphase but also on the temperature profile applied to the sizing before composite fabri...

Cure behavior of an epoxy resin was investigated at different cure temperatures (110, 120, 130, 140, and 150°C) and cure times in the presence of 2 wt% of an N-benzylpyrazinium hexafluoroantimonate (BPH) cationic catalyst by means of differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The glass transition temperature (T g ) and chemical conversion (x) at the different temperatures were determined from DSC thermograms. TheT g andx vs. ln time data were superposed up toT g = 100°C andx = 0.70 by shifting horizontally at a reference temperature ofT g = 130°C. It is interesting that theT g andx of the superposed data increase rather slowly in the early stage of cure and rapidly thereafter. Therefore, the increase of theT g andx can be divided into two regions;R I = −18.4(=T g ) ∼ 5°C andR II= 5 ∼ 100°C inT g , andR I = 0 ∼ 0.24 andR II= 0.24 ∼ 0.70 in x. TheR I is closely related to the initiation reactions between BPH and epoxy and between hydroxy group and epoxy in this epoxy/catalyst system. From the kinetic analysis of theT g -shift, activation energy was 12.5 kcal/mol. The relationship betweenT g andx was also considered. The gelation and vitrification times for different cure temperatures were obtained from DMA curves.

Lithium air batteries have been recognized as one of expected next-generation military power sources, supplying power for a long time even in independent extreme environment. For the commercialization of lithium air batteries, it is essential to search for a cathode material capable of stable and efficient on electrochemical reaction at the interface with the electrolyte. Among the numerous cathode materials, such as carbon nanostructures, expensive noble material, and metal oxides, carbon-based materials are intensively researched as candidate oxygen electrode for lithium air batteries thanks to the engineering pore size and the competitive cost. However, they suffer from degradation of the carbon structure due to the formation of side products limiting the benefit of theirs oxygen reduction reaction characteristic. Recently, molybdenum sulfide(MoS2) has been received the attention as a promising catalyst to maximize oxygen reduction and evolution reactionon the carbon-based cathode. In this study, various shaped MoS2 were grown on activated carbon felt, and their electrochemical properties were compared and analyzed in order to attain a way to maximize the electrochemical reaction in electrode. We also investigated the structure and microstructure of the electrodes before and after discharge test to understand the relation between the performance of cathode materials under various synthesis condition of the catalyst for lithium air batteries.

The oxygen electrode is the most important part in lithium air batteries for oxygen reduction and evolution reaction (ORR/OER) in order to get closer to the theoretical energy density of 11,238 Wh/kg, which is the best among the batteries ever developed. Many carbon materials have been researched as a candidate oxygen electrode for lithium air batteries such as a carbon black, CNTs and 2D graphene. Compared to the many research results, there are still many controversies on optimum oxygen electrode for lithium air batteries. The most important properties for oxygen electrode are the microstructures such as an optimum pore size of less than 10 nm and pore size distributions which affect greatly to ORR/OER at the interface of between the electrode and electrolyte. In this perspective, the hydrothermally self-assembled 3D RGO has great potential as an oxygen electrode. Because, it has a wide range of pore size and large surface area, as well as a high conductive network. However, 3D RGO has some obstacle to be surpassed such as side reactions which induce a large voltage gap, and decay the cycling performances. If the electrochemical reaction mechanisms of 3D RGO in lithium air batteries are well investigated clearly, the 3D RGO is a still desirable electrode for lithium air batteries. In this research, we synthesized self-assembled 3D RGO electrode by means of hydrothermal methods. The electrochemical properties and reaction mechanisms of the self assembled 3D RGO electrode were investigated using BET, EIS, SEM, XRD. As a result, we carefully assessed the possibility of 3D RGO as a game changer in lithium air batteries.

Lithium-air batteries(LAB) utilize oxygen from the air as a cathode active material and pure metal lithium as an anode. Recently, LAB have attracted much interest due to their high theoretical energy density over lithium-ion batteries. However, most of the R&Ds are in their early stages. The main obstacle of LAB for real-life application is cathode, which commonly use carbon materials such as super-P, carbon black. Super-P, among the carbonaceous cathode materials for LAB, reported good performances in specific energy density because of its unique meso porous structure. In this study, the effect of the transition metal dichalcogenide(TMDC) additives in carbon electrode on th electrochemical performances of LAB is evaluated. On a LAB during discharge, the lithium in the anode is oxidized to lithium ions(Li+). Li+ are transported through the electrolyte to catode and react with oxygen. The oxygen combines with metal ions from TMDC, that prevent generating of lithium Oxide(Li2O) and lithium peroxide(Li2O2) in the cathode. In this research, TMDC additives(e.g. MoS2, WS2) in carbon black cathode were prepared and then assembled into coin cell(CR2032). The discharge performances according to the weight percentage of TMDC in carbon black were investigated. Microstucture and electrochemical characteristics of the discharged cathode and pristine cathode were analyzed by XRD,SEM and EDS.

The imidization and cure reactions of a thin film of phenylethynyl imide oligomer (LaRC PETI-5, M n =2500 g/mol ) applied to a glass fabric and processed under cumulative and isothermal heat-treatment conditions have been measured. Three distinguishable peaks were detected in the tan δ curves, which give useful information on the glass transition temperature, imidization temperature, and cure reaction temperature. The degree of imidization or cure reaction occurring during the cumulative and isothermal cure processes is related to the presence and size of the imidization peak and the cure reaction peak. The rate of cure increases substantially above 250°C. The T g of the fully cured LaRC PETI-5 was measured as 287°C. The maximum in the tan δ curve transformed with increasing cure temperature from a triplet due to completion of imidization above 250°C to a singlet after completion of the cure reaction. The maximum of the singlet tan δ curve at 287°C is identified as the T g of the LaRC PETI-5 polyimide. It is concluded that the dynamic mechanical behavior of LaRC PETI-5 strongly depends on thermal history, especially above 300°C. This result also confirms that after cumulative or isothermal processing, LaRC PETI-5 can be fully cured at 350°C for 1 h. These results agree well with the Fourier Transform infrared spectroscopy and differential scanning calorimetry results reported earlier.