Low Surface Area Carbon Research Articles

Gas adsorption analysis for quantifying the edge sites of graphite

The edge plane exposed on the surface of carbon materials is the active site that determines their properties. When graphite is used as the negative electrode in lithium-ion batteries, the edge plane acts as an access point for lithium insertion/desorption. However, because of the low specific surface area and amorphous carbon coating of graphite particles, accurately estimating the number of edge planes is challenging. Therefore, we propose a technique for determining graphite edge planes based on the stepwise adsorption of Kr onto the hexagonal carbon network surface. Graphite particles with highly modified surface structures were prepared by controlling the particle size, heat treatment temperature, and amorphous carbon coating. Electrochemical evaluation revealed significant differences in charge-transfer resistance, an indicator of edge planes. The edge plane determination results obtained using conventional methods such as X-ray diffractometry and Raman spectroscopy did not correlate well with charge-transfer resistance. Meanwhile, Kr adsorption measurements revealed that the stepwise adsorption behavior, because of the interaction of Kr with the energetically homogenous surface, varied significantly depending on the surface properties of graphite particles. The number of edge planes estimated by gas adsorption strongly correlated with charge-transfer resistance. Consequently, we determined that the graphite edge plane tied to the electrochemical index can be derived using gas adsorption analysis. This edge plane determination technique would be applicable not only to graphite but also to highly crystalline carbon materials with an exposed hexagonal carbon network surface.

Stability of Ruthenium/Carbon Catalytic Materials during Operation in Carbon Monoxide Methanation Process

The stable activity of catalysts is an important characteristic, which determines their suitability for industrial applications. The purpose of this study was to investigate the stability of ruthenium systems deposited on carbon under conditions simulating long-term operation in CO methanation. Two series of Ru/carbon catalysts were prepared and studied during CO methanation in a hydrogen-rich gas stream. Two graphitized carbons substantially differing in their surface area (23 and 1457 m2/g) were used as supports, and Ru loadings of 3 and 6 wt.% were applied. The stability of Ru/C catalysts was examined in a 240 h time-on-stream test. The samples were characterized by CO chemisorption, XRD, TEM, Raman spectroscopy, TG–MS studies and CO-TPD. The stability of the catalysts over 240 h in the CO + H2 mixture depended on the support type and Ru loading. The highest CO conversion and increased activity was observed for both catalysts with Ru dispersion above 80%. The tested systems were also resistant to carbon deposition. Interestingly, a similar level of activity was obtained for 3 wt.% Ru supported on the low surface area carbon. It is presumed that the similar activity observed for systems with such different ruthenium dispersion is related to the presence of active sites of different strength and structure on the surface of both small and large Ru particles.

New insights into the performance analysis of flow-electrode capacitive deionization using ferri/ferrocyanide redox couples for continuous water desalination

Flow Electrode Capacitive Deionization (FCDI) is a promising technology that uses carbon materials as flow electrodes in aqueous conditions to enable continuous desalination. In this work, the parametric investigation of the FCDI cell was carried out for low and high surface area activated carbon. When 1 mM/1 mM ferri-/ferrocyanide redox couple in the 1 M NaCl supporting electrolyte containing the 5 wt% high surface area activated carbon and 0.5 wt% MWCNT is circulated as flow electrode at the flow rate of 8 mL/min in the electrode chamber and 0.1 mM NaCl feed water is circulated in single-pass mode at 8 mL/min, the FCDI system achieved a significant improvement in desalination performance up to 76.38 % of SRE, with a high average salt removal rate of 43.925 µg/cm2s @ 2 V, charge efficiency of 20.11 % and average energy consumption of 0.27 kWh/mol, through a thorough parametric investigation. When the FCDI cell was tested with tap water, the average salt removal rate, average energy consumption, and salt removal efficiency were calculated at 6.11 μg/cm2s, 2.46 kWh/mol, and 46.61 % respectively, resulting in the reduction of total dissolved solids of 600 mg/L at the inlet to 365 mg/L at the outlet. The combination of microporous high surface area carbon and ferro-ferri redox couple propelled the desalination performance in comparison with the macroporous low surface area carbon, maximizing the ion removal rate, which further reduced the energy consumption and operating voltage for the process.

Tolerance of Silicon Oxide‐Coated Pt/C Catalyst Toward CO and H2S Contamination in Hydrogen for Proton Exchange Membrane Fuel Cells

Platinum on graphitized low surface area carbon (Pt/C) is coated with a silicon oxide thin film and is employed as anode catalyst to manipulate the tolerance of proton exchange membrane fuel cells toward carbon monoxide and hydrogen sulfide contamination. The SiO2 coating, prepared by successive hydrolysis of 3‐aminopropyl‐triethoxisilane and tetraethoxysilane, forms clusters in proximity to Pt in sizes comparable to the catalyst particles, leaving most of the carbon surfaces free. The performance with and without CO is investigated in situ at relative humidities (RH) of 100%, 70%, and 40%. When operated with neat hydrogen, SiO2‐Pt/C shows marginally better performance owing to an improved protonic conduction due to the water retaining hydrophilic SiO2. Upon operation with CO‐contaminated fuel, the SiO2‐Pt/C performs worse than that of Pt/C particularly at high RH. CO stripping measurements reveal an increase in CO oxidation potential for the SiO2‐Pt/C, suggesting an increased CO coverage and consequently higher anode overpotentials during operation with CO‐contaminated fuel. Upon operation with H2S in the fuel, the SiO2 coating extends the lifetime until the cell voltage broke down, which is attributed to the enhanced water retention due to SiO2 and the solubility of sulfuric species.

Expandable polystyrene waste modified iron sludge-based biochar activating multiple free radicals for deep wastewater treatment

Fe-containing sludge can be converted to functional biochar as a promising resource recycle pathway. However, activating properties of Fe sludge-based biochar are always limited by low specific surface area and weak carbon center for persistent free radical(PFRs). In the current study, waste expandable polystyrene particles were simultaneously used to improve the biochar catalytic performance. The co-prepared biochar achieved a high micromesoporous ratio(98.4%) with specific surface area (345.3 m²/g), improved by 20.1% and 105.2% than unimproved biochar. The improved micromesoporous properties performed better iron active sites and oxygen-containing functional groups for PFRs functioning in wastewater. The co-prepared biochar showed an efficient catalytic degradation through persulfate activating multiple free radicals of 1O2, O2˙ˉ, ˙OH and SO4˙ˉ, which removed 95.4% sulfamethoxazole with mineralizing ratio of 74% within 60 min. The recycling of waste iron sludge and waste polystyrene foam material can achieve functional biochar to apply in deep treatment of refractory organic wastewater.

Enhancing Voltage Reversal Tolerance of Proton Exchange Membrane Fuel Cells by Tuning the Microstructure of IrOx Catalysts.

Voltage reversal of proton exchange membrane fuel cells caused by hydrogen deficiency seriously deteriorates the anodes and lowers their performance and lifetime. A commonly used method is to add oxygen evolution reaction catalysts (e.g., IrO2) to the anode to extend the water electrolysis plateau against harmful carbon corrosion. Herein, strongly connected IrOx nanoparticles (SC-IrOx) are prepared by removing the low surface area carbon carrier of the as-synthesized Ir/C catalyst. The reversal-tolerant anode with SC-IrOx owns an anti-reversal time of 9.32 h, which is 3.2 and 4.4 times that of the reversal-tolerant anode with commercial IrOx and weakly connected IrOx, respectively. Further transmission electron microscope characterizations reveal that SC-IrOx can construct a stable electron and proton transport pathway in the anode catalyst layer, which can delay the isolation of oxygen evolution reaction catalyst from the electron and proton conducting network, thus extending the water electrolysis plateau. Herein, our findings suggest that tuning the microstructures of IrOx catalysts is indeed an effective and promising approach to extend the water electrolysis plateau and alleviate the performance degradation of proton exchange membrane fuel cells during the voltage reversal process.

Understanding the Role of Carbon Mixtures on the Polarization of Sulfur Electrodes in Lithium-Sulfur Batteries

The performance of the sulfur-carbon composite cathode in a lithium-sulfur battery is chiefly determined by the nature of the carbon materials, the total sulfur content, and the distribution of sulfur within the composite electrode. Despite years of research, the role of these major factors in achieving optimal cathode performance is not well-understood. The present study uncovers the factors arising from formulation and processing that contribute to the internal resistance and rate capability of Ketjenblack-carbon based sulfur cathodes. Despite its enormous surface area, Ketjenblack-carbon-based sulfur electrodes exhibit surprisingly poor discharge rate capability and a high polarization resistance, providing no more than 180 mAh g−1 at the C/20 rate and delivering a high specific capacity of 1200 mAh g−1 only at a very low discharge rate of C/50. Our studies uncovered that a large contribution to the polarization resistance that arises from inter-particulate contacts and charge-transfer processes occurred close to 30% depth of discharge whereupon sulfur formed thick insulating sheets on the Ketjenblack particles, requiring an additional electron-percolation pathway for reducing the polarization. By the addition of a low-surface area carbon, Super-P®, such an electron conduction pathway could be achieved; the internal resistance of the Ketjenblack cathode decreased by four times and the electrode delivered an impressive capacity of 950 mAh g−1 at C/5 rate. We anticipate that the detailed analysis of impedance and the new learnings from this study will provide the insight needed for improving the formulation and design of the sulfur cathode.

Experimental analysis of CO2 reduction using low surface area carbon beads (CB) and Ca/CB catalyst by thermocatalytic gasification for fuel gas production

Experimental analysis of CO2 reduction using low surface area carbon beads (CB) and Ca/CB catalyst by thermocatalytic gasification for fuel gas production

Integration of a high oxygen permeability ionomer into polymer electrolyte membrane fuel cell cathodes for high efficiency and power density

In this work, we present a study on the integration of a high oxygen permeability ionomer (HOPI) with high durability carbon supported platinum (Pt/C) catalysts to prepare cathode catalyst layers (CCLs) for polymer electrolyte membrane fuel cells (PEMFCs). A key motivation is the production of PEMFCs with high efficiency and durability for heavy-duty fuel cell vehicles. Our results from integrating a pre-commercial HOPI with robust, state-of-the-art catalysts with medium and low surface area carbon supports show significant increases in specific activities (67% increase over the standard commercial ionomer) at low current densities and reduced oxygen (O2) transport resistances (RO2’s) at high current densities, enabling both higher efficiency and peak power density. The reduction in the RO2 with the HOPI is most significant at low relative humidity (RH), due to its more rigid backbone structure resisting compaction at lower water contents. In our ink optimization analysis, we show that the HOPI in this study achieves its peak performance with an ionomer to carbon ratio (I/C) of 0.6 and a moderately alcohol-rich ink solvent when fabricating catalyst layers by the decal method with an automatic wet film coater.

Catalyst layers for fluorine‐free hydrocarbon PEMFCs

Herein, we study catalyst ink composition on the current-voltage characteristics of fuel cells incorporating fully hydrocarbon-based membrane-electrode-assemblies. The membrane and ionomer used for these studies is sulfo-phenylated poly(phenylene) biphenyl (sPPB-H+). Fuel cell current-voltage characteristics vary depending on the nature of the dispersing medium of the ink with single-cell power densities increasing for inks prepared from MeOH > EtOH > iPrOH, based on 3:1 alcohol:water mixtures. This correlates with the catalyst layer's higher BET- surface area, porosity, electrochemically active surface area (ECSA), and lower cathodic charge transfer resistance. Despite this, MeOH-based catalyst inks yield catalyst layers with relatively high ionic resistance, which is postulated to result from the poor integrity of ionomer films coating C/Pt aggregates within the catalyst layer. This deficiency is mitigated using low surface area Vulcan XC-72 catalyst support. Using low surface area carbon supports, a satisfactory proton conduction network can be established in the catalyst layer with ionomer contents as low as 2.5 wt% (∼0.023 mgionomer cm-2), with a > 10% increase in peak power density (H2/Air) compared to a conventional D520-Nafion®-based MEA containing 30 wt% ionomer in the catalyst layer (∼ 0.28 mg cm-2).

Functionalization of carbons for Pt electrocatalyst in PEMFC

One of the limitations of conventional carbon-supported Pt electrocatalyst in Proton Exchange Membrane Fuel cell (PEMFC) is the carbon corrosion during start-up and shut-down of a fuel cell. The present work investigates the stability of three different carbon blacks and their functionalized forms as supports for Pt electrocatalysts. Acetylene black (AB) as a low surface area carbon shows a higher degree of graphitization and effective functionalization than Vulcan carbon and Ketjan black. Electrochemical tests on corrosion studies show that the AB and its functionalized form (f-AB) as support for Pt electrocatalyst exhibits good electrochemical activity with an ECSA of 52 m2g-1 and 78 m2g-1 and excellent corrosion resistance with minimum ECSA loss of 6% and 16% for Pt/AB and Pt/f-AB, respectively, satisfying the DoE target (<40% ECSA loss.) This makes the Pt/f-AB a promising durable electrocatalyst for PEMFC with improved activity and durability.

Fuel Cell Automotive Drive-Cycle Cathode Catalyst (Pt/C) Layer Durability: Dependence on Low Vs. High Carbon Supports and Ionomer-to-Carbon-Ratio

The typical urban automotive drive-cycle for proton exchange membrane fuel cells (PEMFC) consists of frequent idle-to-peak power cathode voltage transients, with extremes ranging from 1.2 V to 0.6 V, respectively. Understanding the platinum electrochemical surface area (ECSA) loss mechanisms dependence on material and operational conditions have been extensively investigated with the objective of minimizing performance losses over the lifetime of PEMFC powered automobiles. Commonly, automotive accelerated stress tests (AST) are performed ex-situ on thin catalyst films. The standard catalyst consists of carbon supported platinum nanoparticles (Pt/C). This study compares triangle waveform (TW) ASTs monitoring ECSA loss for ex-situ (thin film in 0.1 HClO4) and in-situ (catalyst layers bond with ionomeric electrolyte in a complete membrane electrode assembly (MEA)). The ionomer-to-carbon ratios (I/C) of the MEAs is varied from 0.6 to 1.5 on either low surface area carbon (LSAC) or high surface area carbon (HSAC) supports. The AST profiles included 25k cycles at 10 sec intervals, between the upper potential limit of either 0.9 V or 1.2 V and the lower potential limit of 0.6V, with intermediate ECSA evaluations from the H-desorption current (0.02 V → 0.4 V).The electrolyte environment alters, liquid vs. ionomer, the dominant AST decay mechanism, Figure 1A. The decay in the liquid electrolyte is most sever upon initiation of the AST and the rate of decay decrease after the first 2000 cycles. While the MEA decay is less initial, but maintains the same rate of initial decay over 5000 cycles resulting in a higher overall loss of ECSA. ECSA decay is exacerbated at temperatures of 70°C. Increasing the I/C increases the interfacial acidity at the surface of the Pt/C and results in exacerbated ECSA loss, Figure 1B. In accordance with the Pourbaix diagram for Pt, it is less stable in a more acidic environment. The relative rate of ECSA loss is reduced on HSAC supports. Figure 1

Unsupported CoNixMo sulfide hydrodesulfurization catalysts prepared by the thermal decomposition of trimetallic tetrabutylammonium thiomolybdate: effect of nickel on sulfur removal

Herein we report the synthesis of unsupported bimetallic CoMo and trimetallic CoNiMo sulfide catalysts prepared by thermal decomposition (ex situ activation) of carbon-containing precursors and varying the nickel concentration for the hydrodesulfurization (HDS) of dibenzothiophene. The catalysts prepared were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, inductively coupled plasma mass spectrometry and BET surface area measurements. The results from the characterization showed that the addition of an alkyl chained precursor results in non-porous catalysts with low surface area and high carbon content, which negatively affects the formation of crystalline phases such as molybdenum sulfide and their performance in the HDS reaction. Furthermore, the addition of nickel has a negative effect on the catalysts since it was observed that when it was added, the reaction rate values decreased and the catalyst with the highest catalytic activity turned out to be the CoMo catalyst. Although nickel catalysts generally have more affinity for hydrogenation reactions, unsupported trimetallic catalysts showed a preference for the direct desulfurization pathway.

Modeling Oxygen Transport in High Surface Area Carbon Supports for Polymer-Electrolyte Fuel Cells

An analytical model for resistance to oxygen transport in air electrodes containing carbon black supports with high surface area was developed by combining a Thiele modulus—effectiveness factor approach at the agglomerate scale (∼150 nm) with nanoscale diffusional resistance in carbon micropores/pits (∼5 nm). This paper extends an earlier model for transport resistance to platinum nanoparticles on low surface area carbon. Differences in transport resistances between catalyst layers with high and low surface area carbon blacks predicted by the model with reasonable geometric dimensions and physical properties are consistent with experimental observations.

Carbon Black Flow Electrode Enhanced Electrochemical Desalination Using Single-Cycle Operation.

Flow-electrode electrochemical desalination (FEED) processes (e.g., flow-electrode capacitive deionization), which use flowable carbon particles as the electrodes, have attracted increasing attention, holding the promise for continuous desalination and high desalting efficiency. While it is generally believed that carbon particles with abundant microporous and large specific capacitances (e.g., activated carbon, AC) should be ideal candidates for FEED electrodes, we provide evidence to the contrary, showing that highly conductive electrodes with low specific surface area can outperform microporous AC-based electrodes. This study revealed that FEED using solely high surface area AC particles (∼2000 m2 g-1, specific capacitance of ∼44 F g-1, average salt adsorption rate of ∼0.15 μmol cm-2 min-1) was vastly outperformed by electrodes based solely on low-surface area carbon black (CB, ∼70 m2 g-1, ∼0.5 F g-1, ∼0.75 μmol cm-2 min-1). Electrochemical impedance spectroscopy results suggest that the electrode formed by CB particles led to more effective electronic charge percolation, likely contributing to the improved desalination performance. In addition, we propose and demonstrate a novel operation mode, termed single cycle (SC), which greatly simplified the FEED cell configuration and enabled simultaneous charging and discharging. Using SC mode with CB flow electrodes delivered an increased average salt removal rate relative to the more traditional short-circuited closed cycle (SCC) mode, achieving up to 1.13 μmol cm-2 min-1. Further investigations demonstrate that up to 50% of energy input would be avoided when using CB flow electrodes operated under SC mode as compared to that of AC flow electrodes operated under SCC mode. In summary, the FEED process presented in this study provided an innovative and promising approach toward high-efficient and low-cost brackish water desalination.

Modeling Water Uptake and Pt Utilization in High Surface Area Carbon

Reducing the loading of expensive Pt-based catalysts in polymer-electrolyte fuel-cell (PEFC) catalyst layers (CLs) is imperative for wide-scale commercialization. However, a local resistance close to the Pt reaction sites becomes significant at low Pt loadings and hinders adequate performance.1,2 In our previous study, we demonstrated that the local resistance is primarily related to the proton-conducting ionomer thin-film within the CL and consists of: (i) reactant transport resistance due to low permeability of ionomer thin-film (compared to bulk ionomer) and (ii) interfacial resistance due to Pt/sulfonic-moiety interactions.3 Thus, there is need to optimize ionomer design to minimize CL resistance.In this talk, we investigate the impact of ionomer chemistry, content, and equivalent weight (EW) on CL resistance. Using H2 limiting-current measurements, the total CL resistance is segregated into transport and interfacial components. CL resistance increases monotonically with ionomer content, primarily due to thicker ionomer films. Low EW ionomers demonstrate higher interfacial resistance due to high density of sulfonic groups, whereas higher EW ionomers exhibit higher transport resistance due to low-reactant permeability associated with low-water uptake. These findings are rationalized through comparison of properties and structure/function relationships elucidated by ionomer thin-film studies on planar substrates, thus bringing together model and in-situ studies. Further, time-permitting, the impact of carbon support (low versus high surface area carbon) on local CL resistance will also be discussed, mainly via modeling water uptake and proton pathways. Overall, the knowledge gained demonstrate pathways towards ameliorating the local resistance and enabling high performing low Pt-loaded PEFCs. Acknowledgements We would like to thank Sarah A. Berlinger and Robert Darling for helpful discussions. This work was funded under the Fuel Cell Performance and Durability Consortium (FC-PAD) funded by the Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office, of the U. S. Department of Energy under contract number DE-AC02-05CH11231.

HNBR-based composite for seals used in coolant fluids: Swelling related to different silicates at high temperature

The effects of five fillers (two synthetic calcium silicates, one natural calcium silicate, talcum and a low specific surface area carbon black) filled with hydrogenated acrylonitrile butadiene rubber (HNBR) for possible use in seal for coolant fluids were developed by hardness, mechanical properties and hot air aging properties. Fluid blends were used to simulate the degraded OAT coolant. The swelling mechanism of HNBR vulcanizates was investigated by XRD, SEM, EDS, FT-IR and GC-MS. The results indicated that the filler with high specific surface area was easier to combine with HNBR. Hot air aging tests revealed a relatively high heat resistance and can meet the practical requirements. 2-ethylhexanoic acid hydrolyzed by sodium 2-ethylhexanoate as corrosion inhibitor react with silicate fillers in rubber to form 2-ethylhexanoate into the coolant, thus the network structure of rubber destroyed, while 2-ethylhexanoic acid and ethylene glycol diethyl-hexanoate as well as a small amount of ethylene glycol and water immersed into rubber. Higher crystallinity and lower specific surface area made natural CaSiO3 an efficient intrinsic base reserve to scavenge acidic products and effectively reduce the swell of filled HNBR.

Hard carbons derived from green phenolic resins for Na-ion batteries

Hard carbons have become recently one of the most promising classes of anode materials for sodium ion batteries (NIBs) owing to their high specific capacity and good cycling stability. Among the precursors used to prepare hard carbon, phenolic resins are of great interest due to their high carbon yield, however, their toxicity must be overcome. In this paper, we propose a green, simple and scalable procedure to obtain phenolic resins which by pyrolysis at high temperature (>1000 °C) result in eco-friendly hard carbons with low surface area, disordered structure and high carbon yield. The influence of several synthesis parameters (type of solvent, thermopolymerization/annealing temperature and gas flow) was studied to determine the impact on both phenolic resin and hard carbon characteristics. The synthesis time (12 h-3 days) was found to depend on the used solvent whereas the carbon yield (25–35%) on the cross-linking degree which could be controlled by adjusting both thermopolymerization temperature and atmosphere. The structure of the hard carbons mainly changed with the carbonization temperature (1100–1700 °C) while the texture of the material was sensitive to most of the studied parameters. Stable reversible capacity up to 270 mAhg−1 and 100% coulombic efficiency (CE) after few cycles are obtained, demonstrating the potential for Na-ion applications.

Influence of Metal Oxide Coatings, Carbon Materials and Potentials on Ion Removal in Capacitive Deionization

Metal oxide coated carbon materials were shown to have increased ion removal over many of the uncoated carbons when used in capacitive deionization; however, the influence of the coating was dependent on the carbon material used as the substrate. Specifically, four different carbon materials, coated and uncoated, were tested. During removal, the negative electrode was coated with SiO2 and the positive with γ-Al2O3. The SiO2 coatings improved Ca2+ removal for 3 of the 4 carbon materials tested and the γ-Al2O3 coatings improved Cl− removal for 2. The mechanism for this increase in removal appeared to be carbon dependent, and could be associated with the addition of new surface groups, improved wettability, or for the low surface area carbon, an increase in specific surface area of the composite material. Moreover, it was also shown that the surface area of the carbon material was not the only factor that determined the electrosorption capacities of the electrode. In addition, certain electrodes had large improvements in ion removal with increases in the applied potential. However, the stability of the electrodes, as well as faradaic reactions that may evolve at high potentials, must be considered when increasing the potential to improve ion removal.

Interfaces Promoted Conversion-Type Reactions for Energy Storage

Conversion-type reactions based battery chemistry presents a great promise for next-generation energy storage. It is based on using the chemical reaction (also called chemical transformation) of the working ion to store energy, different than intercalation-type reactions as used in today’s Li-ion batteries. Good examples include Li-S, Li-O2, and broadly speaking metal electrodes (Li, Mg, Zn, etc.). Interfaces generally play a more crucial role in these battery chemistry systems because of the complexity of this type of reaction even though each of the systems has its unique characteristics. This not only includes electrode/electrolyte interfaces, but also the interfaces within the electrode materials. Here, we use two examples of battery chemistry to demonstrate how the manipulation of interfaces can promote the conversion-type reactions for energy storage: Mg chemistry and Li-S chemistry. In Mg battery chemistry, due to the divalent nature of Mg2+, the ion transport kinetics in solid host materials is limited. Therefore, the development of Mg battery has been limited by poor performance of electrode materials. We have developed two conversion-type electrode materials with improved Mg2+ storage performance: SnSb alloys for anode1 , 2 and V2O5 nanoclusters for cathode.3 More importantly, our experimental and theoretical modeling reveal that the interfaces between the multicomponent phases generated during repeated magnesiation–demagnesiation is responsible for the improved performance of SnSb; a surface-controlled reaction of Mg2+ and V2O5, denoted as a molecular energy storage mechanism, improves the reaction kinetics which increases the rates and capability. In Li-S battery chemistry, control of solution chemistry and nucleation of polysulfides (on cathode host surface) is crucial for improved capacity and cycling stability. We have demonstrated that, through tuning the solubility of polysulfides in electrolytes, an improved cycling stability is achieved. The controlled nucleation of polysulfides on carbon nanofiber surface leads to the formation of a unique porous microsphere structure of Li2S. This unique porous Li2S microsphere enables a close to 100% utilization of S (specific capacity >1600mAh/gS); it also decreases the passivation of cathode. This opens up a new avenue for Li-S R&D of using low surface area carbon host materials, thus a great potential for high pack density and low electrolyte/sulfur ratio in Li-S cells. In this talk, we will present our understanding on these interface-related conversion-type reactions and recent progress of material innovation that improves device performance. New electrode architecture engineering will also be discussed. 1. Y. W. Cheng, Y. Y. Shao, L. R. Parent, M. L. Sushko, G. S. Li, P. V. Sushko, N. D. Browning, C. M. Wang and J. Liu, Adv. Mater., 2015, 27, 6598-6505. 2. L. R. Parent, Y. W. Cheng, P. V. Sushko, Y. Y. Shao, J. Liu, C. M. Wang and N. D. Browning, Nano Lett., 2015, 15, 1177-1182. 3. Y. W. Cheng, Y. Y. Shao, V. Raju, X. L. Ji, B. L. Mehdi, K. S. Han, M. H. Engelhard, G. S. Li, N. D. Browning, K. T. Mueller and J. Liu, Advanced Functional Materials, 10.1002/adfm.201505501, 2016.