Electrochemical Performance Characterization Research Articles

Performance Optimization of Supercapbattery with Porous Modification on Silicon as Anode and Cathode Based on Al<sub>2</sub>O<sub>3</sub>/CuCrO<sub>2</sub>

The development of the supercapbattery has become the focus of energy storage research due to their potential to increase energy and power density. This research is focused on developing a modification of silicon (Si) porous as an anode with Al2O3/CuCrO2/AC composite as a cathode of supercapacitor. These electrodes were synthesized using LA133 binder with deionized water as solvent. The supercapacitor electrode uses an aluminum foil substrate, while the Si electrode uses a cupper foil substrate. The structural and morphological characterization of the electrodes were identified through XRD, FTIR, and SEM tests, while the electrochemical performance characterization using Galvanostatic Charge-Discharge (GCD) instruments. The results of XRD data analysis of thin film electrodes of supercapacitor showed diffraction peaks which indicated the phases Al2O3/CuCrO2/AC and Si porous. The absorption functional groups of Al2O3/CuCrO2/AC and Si porous were identified through FTIR characterization. The results of SEM showed the addition of CuCrO2 and structure modification of silicon into porous caused increasing value of porosity. The electrochemical performance of the optimum point at Al2O3/CuCrO2/AC condition, showing a specific capacitance of 50.3 F/g, an energy density of 36.499 Wh/kg, and a power density of 433.6 W/kg. The combination of Al2O3/CuCrO2/AC//Si Porous 16 for supercapbattery devices shows performance with a specific capacitance of 14.4 F/g, an energy density of 6.1 Wh/kg, and a power density of 33.6 W/kg. These results indicate an increase in electrochemical performance compared with Si anodes without modification.

Preparation and Electrochemical Performance of Activated Composite Carbon Nanofibers Using Extraction Residue from Direct Coal Liquefaction Residue

Organic carbon extracted from direct coal liquefaction residue (DLCR) is an ideal precursor for the preparation of carbon materials. However, investigations into the utilization of the extraction residue (ER) are rarely reported. In this work, ER from DCLR was pretreated with H2O2 to afford oxidized extraction residue (OER). Then, the OER was mixed with polyacrylonitrile (PAN) in N,N-dimethylformamide for the preparation of composite carbon nanofibers by electrospinning. With adding 80 wt.% OER, the composite carbon nanofibers still demonstrate a clear fiber profile and smooth surface under a scanning electron microscope, indicating that the OER has good solubility with PAN in N,N-dimethylformamide. The electrochemical performance characterization of the activated composite carbon nanofiber shows that the P-OER60-AC (activated composite carbon nanofibers prepared with 60 wt.% of OER and 40 wt.% of PAN) has a better electrochemical performance with a specific capacitance of 97 F/g at 0.5 A/g, as compared to the others. Additionally, the P-OER80-AC (activated composite carbon nanofibers prepared with 80 wt.% of OER and 20 wt.% of PAN) is also considerable for the perspective of coal-based solid waste treatment and utilization.

Coupling ultrafine TiO2 within pyridinic-N enriched porous carbon towards high-rate and long-life sodium ion capacitors

Coupling TiO2 within N-doped porous carbon (NPC) is essential for enhancing its Na+ storage performance. However, the role of different N configurations in NPC in improving the electrochemical performance of TiO2 is currently unknown.In this study, melamine is deliberately incorporated as a pore-forming agent in the self-assembly process of metal organic framework precursors (NH2-MIL-125(Ti)). This intentional inclusion of melamine leads to the one-pot and in-situ formation of highly active edge-N, which is vital for the development of TiO2/NPC with exceptional reactivity. Electrochemical performance characterization and density functional theory (DFT) calculation indicate that the interaction between TiO2 and pyridinic-N enriched NPC can effectively narrow the bandgap of TiO2/NPC, thereby significantly improving electron/ion transfer. Additionally, the abundant mesoporous channels, high N content and oxygen vacancies also contribute to the fast reaction kinetics of TiO2/NPC. As a result, the optimized TiO2/NPC-M, with high proportion of pyridinic-N (44.1 %) and abundant mesoporous channels (97.8 %), delivers high specific capacity of 282.1 mA h−1 at 0.05 A g−1, superior rate capability of 177.3 mA h−1 at 10 A g−1, and prominent capacity retention of 89.3 % over 5000 cycles even under ultrahigh 10 A g−1. Furthermore, the TiO2/NPC-M//AC sodium ion capacitors (SIC) device achieves a high energy density of 136.7 Wh kg−1 at 200 W kg−1. This research not only offers fresh perspectives on the production of high-performance TiO2-based anodes, but also paves the way for customizing other active materials for energy storage and beyond.

Investigation of the Impact of Chloride Contamination on Degradation in PEM Water Electrolyzer Cells

Polymer electrolyte membrane water electrolysis (PEMWE) is a promising technology for hydrogen production from renewable energy sources. However, current systems require ultra-pure water (>18 MΩ*cm) and fail in the presence of impurities like dissolved ions or chemical contaminants [1,2]. Due to the cost of purification and local scarcity of groundwater, there is a rising interest in creating electrolyzers that can function using water of inferior quality [3]. Additionally, feedwater used in offshore applications that is generated by the desalination of seawater still contains low amounts of ionic contaminants [4].Among the most detrimental impurities responsible for performance loss in PEMWE, Cl− is present in high concentrations in both, sea- and potable water [3]. Cl− can reduce the efficiency of the electrolysis process by accelerating component degradation and lower the purity of the produced hydrogen. A competing reaction between the oxygen evolution reaction (OER) and the chlorine evolution reaction (CER) results in the formation of gaseous chlorine that lowers the quality of the produced hydrogen gas. Additionally, Cl− blocking layers can form on the catalyst surfaces which result in a reduced electrochemical surface area. For PEM fuel cells, a technology facing related problems, Cl− adsorption has also been reported to accelerate the formation of hydrogen peroxide [5], promoting chemical degradation of the PFSA-based membrane.The scope of this work is to quantify the reduction of efficiency based on different Cl− concentrations in the feedwater of a PEMWE cell. Therefore, a single cell PEMWE with commercial catalyst coated membranes (CCMs) is exposed to different concentrations of Cl−. The PEMWE single cell is operated up to 100 h and investigated by various characterization techniques, including in-situ and ex-situ cell tests. Electrochemical performance characterization by means of polarization behaviour and impedance spectroscopy is carried out throughout a range of currents (0.01 A cm− 2 to 3.0 A cm− 2) at 60°C. Furthermore, the fluoride emission rate (FER) is monitored during the experiments and optical investigation of the CCMs is carried out after the tests. Based on this complementary investigation, a deeper insight into degradation phenomena associated with Cl− contamination in PEMWE cells is presented. Feng, Q.; Yuan, X.; Liu, G.; Wei, B.; Zhang, Z.; Li, H.; Wang, H. A Review of Proton Exchange Membrane Water Electrolysis on Degradation Mechanisms and Mitigation Strategies. Journal of Power Sources 2017, 366, 33–55, doi:10.1016/j.jpowsour.2017.09.006.Kuhnert, E.; Hacker, V.; Bodner, M. A Review of Accelerated Stress Tests for Enhancing MEA Durability in PEM Water Electrolysis Cells. International Journal of Energy Research 2023, 2023, 1–23, doi:10.1155/2023/3183108.Becker, H.; Murawski, J.; Shinde, D.V.; Stephens, I.E.L.; Hinds, G.; Smith, G. Impact of Impurities on Water Electrolysis: A Review. Sustainable Energy Fuels 2023, 7, 1565–1603, doi:10.1039/D2SE01517J.Bacquart, T.; Moore, N.; Wilmot, R.; Bartlett, S.; Morris, A.S.O.; Olden, J.; Becker, H.; Aarhaug, T.A.; Germe, S.; Riot, P.; et al. Hydrogen for Maritime Application—Quality of Hydrogen Generated Onboard Ship by Electrolysis of Purified Seawater. Processes 2021, 9, 1252, doi:10.3390/pr9071252.Katsounaros, I.; Meier, J.C.; Mayrhofer, K.J.J. The Impact of Chloride Ions and the Catalyst Loading on the Reduction of H2O2 on High-Surface-Area Platinum Catalysts. Electrochimica Acta 2013, 110, 790–795, doi:10.1016/j.electacta.2013.03.156.

Electrochemically Oxidized Carbon Nanotube Sheets for High-Performance and Flexible-Film Supercapacitors.

The development of flexible, high-performance supercapacitors has been a focal point in energy storage research. While carbon nanotube (CNT) sheets offer promising mechanical and electrical properties, their low electrical double-layer capacitance significantly limits their practicability. Herein, we introduce a novel approach to address this challenge via the electrochemical oxidation treatment of CNT sheets stacked on a polyethylene terephthalate substrate. This introduces oxygen-containing functional groups onto the CNT surface, thereby dramatically enhancing the pseudocapacitive effect and improving ion adsorption. Consequently, using the material in a two-electrode system increased the capacitance by 54 times compared to pristine CNT. The results of electrochemical performance characterization, including cyclic voltammograms, galvanostatic charge/discharge curves, and capacitance retention testing data, confirm the efficacy of the electrochemical oxidation approach. Furthermore, the mechanical flexibility of the electrochemically wetted CNT sheets was validated through resistance and discharge retention testing under repetitive bending (98% capacitance retention after 1000 bending cycles). The results demonstrate that electrochemically wetted CNT sheets retain their intrinsic mechanical and electrical properties while significantly enhancing the electrochemical performance (0.59 mF/cm2 or 97.8 F/g). This work represents a significant advancement in the development of flexible, high-performance supercapacitors with potential applicability to wearable electronics, flexible displays, and next-generation energy storage solutions.

Efficient biodegradation of trimethoprim and transformation mechanism using the photoelectrocatalytic system

In this study, the coupling of a three-electrode photocatalytic microbial fuel cell system (PMFC) was established for trimethoprim (TMP) degradation, to achieve efficient degradation and electrical energy production simultaneously. The photocatalytic bioanode, degradation performance, electrochemical characteristics and microbial structure were analyzed to explore the degradation of TMP in PMFC. The results showed that rapid degradation and enhanced mineralization of TMP were obtained in the PMFC, which were 1.7 and 1.4 times higher than those of traditional microbial fuel cells (MFCs), respectively. Intermediates in the degradation process were identified in both systems, and three degradation pathways were inferred in the PMFC. The electricity characteristics were investigated and superior electrical production and higher electron transfer efficiency were observed in the PMFC, resulting in a maximum power density of 75.1 mW/m2 and a maximum voltage of 0.225 V. Additionally, the cyclic voltammetry test and electrochemical impedance spectra were used for electrochemical performance characterization, and the results showed the stronger oxidation ability of PMFC with half the charge transfer resistance of MFCs. The microbial community structure demonstrated that the dominant species were enriched and coexisted, involving degradation bacteria, exoelectrogens, and hydrocarbon removal bacterial. Furthermore, canonical correspondence analysis (CCA) revealed a mutual promotion of TMP degradation and electricity production with the involvement of these active genera. In conclusion, this novel technology is an excellent alternative in practical applications for the treatment of wastewater containing antibiotics.

Constructing highly active alloy-perovskite interfaces for efficient electrochemical CO2 reduction reaction

The electroreduction of CO2 through solid oxide electrolysis cells (SOEC) is considered as a promising technology for mitigating climate changes related to global warming. A SOEC system can effectively reduce polarization losses and best utilize process heat to electrolyze CO2 to produce CO. However, this technology is hindered by the sluggish cathode kinetics, which is mainly due to the poor catalytic activity for the CO2 reduction reaction. Herein, this work develops an A-site ordered layered perovskite oxide, (PrBa)0.95Fe1.6Ni0.2Nb0.2O5+δ (PBFNN), as an efficient cathode catalyst for CO2-SOEC. FeNi3 nanoparticles are in situ generated on the surface of perovskite substrate after reduction, the resulting active alloy-perovskite interfaces between FeNi3 and PBFNN substrate can effectively promote the CO2 reduction reaction (CO2RR). The nanoparticles and abundant oxygen vacancies of FeNi3-PBFNN significantly enhance CO2 adsorption and activation, which is verified by the CO2-temperature programmed desorption measurement and density functional theory calculations. Distribution of relaxation time analysis and electrochemical performance characterization indicate that this interface engineering at nanoscale greatly improves the catalytic activity of the cathode for CO2RR.

1D multiphysics modelling of PEM water electrolysis anodes with porous transport layers and the membrane

• 1D novel multiphysics model of a PEM water electrolysis anode is developed. • Two-phase flows with charge conservation are simulated in the anode. • Water management in PEM is investigated for its effects on ion conductivity. • The properties of the porous transport layer are studied for improving performance. • The factors on oxygen evolution reaction are analyzed in CV test simulations. 1D multiphysics modelling of the PEM water electrolysis anode is benefit for detailed investigation of the joint effects of electrochemical performance and multicomponent multiphase flow transport phenomena. Such a model can be effectively applied for the water electrolysis system design and optimization. Recently, the importance of hydraulic effects and dynamic behavior gradually attracts much focus on this specific issue. In this article, a novel 1D dynamic model has been developed for interpreting the multiphysics processes in the PEM water electrolysis anode, which considers the complex fluid dynamics and electrochemistry in the PEM water electrolyzer (PEMWE) components – PEM, the anode catalyst layer and the porous transport layer. As a result, the hydraulic and electrochemical properties of three components were studied for investigation of their effects on the characterization of electrochemical performance and mass transport processes. It concludes that for the improvement of electrolytic performance, the porous transport layer is suggested to be designed for high permeability and low contact angle. The catalyst layer needs to be optimized for its three-phase interface fraction with high coating mass in the membrane assembly.

Crumpled and Eccentric Nanospheres of Ti3C2Tx MXene by Aerosol Jet Printing on Heat Substrate

2D MXene has attracted tremendous attention for developing high‐performance energy storage devices regarding its good metallicity and relatively large accessible surface area. However, the electrochemical performance of MXene‐related devices was hindered due to the pronounced self‐stacking characteristic of MXene. Herein, a convenient aerosol jet printing (AJP) process is developed for the synthesis of MXene nanospheres with crumpled and eccentric structures by modulating the migration and assembly of MXene nanosheets on heat substrate. The existing temperature gradient between the apex and the edge of the deposited droplet causes thermocapillary flows carrying MXene nanosheets toward the edge and the MXene nanosheets are further shaped and assembled along the droplet surface during the solvent evaporation. Interdigital microelectrodes of crumpled MXene nanospheres are tentatively developed for electrochemical performance characterization, a competitive areal capacitance performance is demonstrated in comparison with other MXene‐based devices. Importantly, this work highlights the great potential of the AJP technique for developing functional devices with fascinating hierarchical features as well as further extending applications in miniaturized and intelligent microelectronics.

2D/2D MoS2/g-C3N4 layered heterojunctions with enhanced interfacial electron coupling effect

• 2D/2D MoS 2 /g-C 3 N 4 heterostructures were created via MoS 2 growth in situ. • The heterostructures exhibited enhanced photo- and electro-chemical activities. • The face-to-face contact between MoS 2 and g-C 3 N 4 enhanced interfacial electron coupling. • Broad optical response range and decreased recombination rate of photogenerated carriers improve their performance. 1 T-2H MoS 2 were successfully grown on g-C 3 N 4 nanosheets by convenient two-step calcination and solvothermal process to create two dimensional (2D)/2D heterostructures. 1 T-2H MoS 2 was parallelly grew on g-C 3 N 4 nanosheets to form a stable interfacial heterojunction. Various characteristics confirm the formation of parallel 1 T-2H MoS 2 /g-C 3 N 4 heterostructures. The heterostructures exhibited enhanced photo- and electro-chemical activities. The photocatalytic degradation of dyes and electrochemical performance characterization indicates sample 2.5%MCN with MoS 2 of 2.5 wt% shows excellent photocatalytic activity, in which the degradation rate for rhodamine B (RhB) is 1.84 times compared with pure g-C 3 N 4 nanosheets. Because the face-to-face contact between 1 T and 2H MoS 2 and g-C 3 N 4 forms strong interfacial electron coupling, the optical response range became broad, the photocurrent density increased, and the recombination rate of photogenerated electron and hole decreased. In addition, the formation of 1 T-2H MoS 2 /g-C 3 N 4 parallel heterojunctions and photocatalytic degradation process are studied in detail. The result supplied an efficient approach for the exploration of g-C 3 N 4 based photocatalyst.

Pore Structure Regulation and Electrochemical Performance Characterization of Activated Carbon for Supercapacitors

In order to achieve the purpose of regulating the pore structure characteristics of activated carbon by adjusting the experimental parameters, the effects of carbonization temperature, carbonization time, pre-activation temperature, pre-activation time and impregnation time on the pore structure of sargassum-based activated carbon (SAC) are studied by orthogonal experiment. The gravimetric capacitance of SAC and the relationship between the gravimetric capacitance and specific surface area are also studied. The results show that the SACs prepared at all experimental conditions have developed pore structure and huge specific surface area, reaching 3,122 m2/g. The pore size of SAC is almost all within 6 nm, in which the micropores are mainly concentrated in 0.4–0.8 nm, the mesopores are mainly concentrated in 2–4 nm, and the number of micropores is significantly higher than that of mesopores. During the preparation of SAC, the effect of carbonization temperature on the specific surface area and specific pore volume of SAC is very significant. The effect of carbonization time on the specific surface area of SAC is significant, but the effect on specific pore volume can be ignored. The effects of pre-activation temperature, pre-activation time, and impregnation time on specific surface area and specific pore volume of SAC can be ignored. In addition, SACs show good gravimetric capacitance performance as electrode material for supercapacitors, which can significantly increase the capacitance of supercapacitors and thus broaden their applications. The gravimetric capacitance and specific surface area of SACs show a good linear relationship when the activated carbons have similar material properties and pore size distribution.

Modulating vacancies in nonstoichiometric oxides by annealing polarized nanoporous NiCoMn as thick pseudocapacitive electrode

Thick nanoporous electrode design with pore size in several nanometers can substantially improve the active sites to achieve high energy density. However, the sluggish ion/charge kinetics and mechanical instability limit their rate and long-term cycling capability. To address these obstacles, herein, a thick vacancy-riched nanoporous NiCoMn@oxides (Vo-3DNCM@oxides) core-shell structure as pseudocapacitive electrode in alkaline electrolyte was prepared by polarizing a nanoporous NiCoMn alloy and subsequently mild annealing in Ar atmosphere. As a result, a large number of coordination unsaturated sites can be exposed on active oxide layer by mild annealing. Meanwhile, the nanopores can be coarsened to tens of nanometers. The coordination unsaturated sites synergy with coarsened nanopores can not only endow high-efficient ion/electrons transport channels but also hold the structure stable during fast charge/discharge process. Electrochemical performance characterization illustrates that the 4Vo-3DNCM@oxides electrode annealed at 400 °C shows high capacity retention of about 69.7% at current rates from 1 A cm−3 to upward of 10 A cm−3 (1464 C cm−3 at 1 A cm−3 and 908 C cm−3 at 10 A cm−3) and high energy density of 90.7 mWh cm−3, demonstrating a potential application in pseudocapacitors. More importantly, the novel structural design exhibits promising prospects toward the practical application of integrated thick electrodes.

Boosting Oxygen Evolution Reaction Using Defect Rich Ultra-Thin Ruthenium Oxide Nanosheets in Acidic Media

Hydrogen is regarded as the most promising energy carrier. The pure hydrogen produced from electrochemical water splitting by using renewable energy is the most attractive and effective approach.[1] In comparison to alkaline water electrolysis, proton exchange membrane water electrolyzers (PEMWEs) could operate at higher current densities, lower ohmic loss, more compact system design, faster system response and more stable towards load-cycling and shutdowns. [2] The sluggish kinetics of oxygen evolution reaction (OER) at the anode of PEMWEs has restricted its practical applications. To date, iridium (Ir) metal and its oxide are usually selected as the state-of-the-art catalyst for OER due to their robust and long-term durability under the harsh acidic conditions. Nevertheless, Ir is an extremely scarce element, and its price has been doubled in the past few years. The development of low cost and highly effective electrocatalyst for OER in an acidic medium is urgently needed but remains a great challenge.In this work, we have prepared an ultra-thin RuO2 nanosheets by a simple molten salt method. High resolution STEM results show that the as-prepared RuO2 nanosheets is about 1-2 nm in thickness and hold a large number of defects, like Ru vacancy, grain boundary and amorphous. Toward OER, the as-prepared RuO2 nanosheets demonstrate an outstanding OER activity in acidic electrolyte, with an overpotential of only 199 mV for reach the current density of 10 mA cm-2 geo at a catalyst loading of 125 μg cm-2 geo. At the overpotential of 230 mV, the specific and mass activities of RuO2 nanosheets electrode is up to 0.89 mA cm-2 oxide and 0.516 A mg-1 Ru, which is 14.9 and 80.5 times higher than that of commercial RuO2 catalyst, respectively. Density functional theory (DFT) calculations (Figure 2e and 2f) indicated that the Ru vacancy defect on RuO2 surface could servers as the highly active site for remarkably weaken the binding energies of *O as compared to that of *OOH, which decrease the energy gap between ΔGO and ΔGOOH and thus dramatic enhanced OER performance. We also applied the catalysts in a homemade PEMWE device, at the applied cell voltage of 1.65 V, the current density of the RuO2 nanosheets catalyst cell reaches 0.93 A cm-2, which is almost 3 times larger than that of the cell with commercial RuO2 catalyst (0.31 A cm-2) at the same conditions, demonstrating that the RuO2 nanosheets possess great potential toward developing high performance PEMWEs.This work is under progress. Meanwhile, further characterizations, including XRD, XPS and more detailed morphology and electrochemical performance characterization of the RuO2 nanosheets catalyst will be presented at the meeting.The work described in this paper was financially supported by the Shenzhen Clean Energy Research Institute (No. CERI-KY-2019-003), Shenzhen Peacock Plan (KQTD2016022620054656), Shenzhen Key Laboratory project (ZDSYS201603311013489), The authors acknowledge the assistance of SUSTech Core Research Facilities.

Self‐Supported Binder‐Free Hybrid Electrodes of Cu@CuO Nanowires/Carbon Nanotubes for Supercapacitors with Ultrahigh Areal‐Capacitance

To meet the requirement of clean and efficient energy storage system for practical applications, supercapacitors (SCs), which are promising candidates for the next‐generation energy storage devices, have received tremendous attention. Herein, a hybrid electrode consisting of copper nanowires (Cu NWs) and carbon nanotubes (CNTs) is prepared by simple vacuum‐filtration method. Both Cu NWs and CNTs have excellent conductivities, high aspect ratios, and large surface areas, in which the two kinds of materials are evenly dispersed and are entangled with each other. The electrochemical performance characterization of the Cu@CuO NWs/CNTs hybrid electrode shows high specific capacitance of 1.7 F cm−2 and excellent cycling characteristics of 97.4% after 5000 cycles. The hybrid electrode of Cu@CuO NWs/CNTs with one‐dimensional (1D) structure provides significant advantages in terms of electron/ion transport pathways. The SC devices with excellent electrochemical performance and stability clearly demonstrate their broad applications as low‐cost, high‐performance power supplies for electronic devices.

Detailed insight into processes of reversible solid oxide cells and stacks using DRT analysis

This study demonstrates applicability of the distribution of relaxation times (DRT) methodology to reveal more precise analysis of processes that occur in solid-oxide fuel (SOFC) and electrolysis (SOEC) cells of industrial-size as well as 10-layer stacks. Initially, we show that before starting to interpret the data observed, it is necessary to verify the quality of the impedance data measured in order to be used for further analysis. For the purpose of experimental study, operating parameters were varied and their impact on the system performance was determined. When operating cells and stacks very similar specific frequencies were identified, whereby for the stack one additional peak was observed. In the fuel cell mode the main frequency ranges to link with the processes that occur were identified to be 0.01–5 Hz and 50–100 Hz. In the electrolysis mode, the DRT amplitudes observed are lower, but specific frequencies higher, even by a factor of 10. In addition, specific behaviour of DRT-peaks could be correlated to the morphological changes of the Ni-based fuel electrodes that occurred during the stability tests performed. Summarizing this, the results presented in this study show how to: (i) distinguish different processes, (ii) link the knowledge gained from the analysis of single-cell level and subsequently, (iii) transfer it to real stack system. Thus, this study also represents a guideline for a detailed electrochemical performance characterization of high temperature fuel cell and electrolysis systems using the sophisticated DRT tool.

(Invited) Thiophosphate Based Solid Electrolytes and Cathodes Interfaces

Stable high ion-conducting solid electrolytes are enablers for all solid state batteries. Among many class of materials, Lithium thiophosphate family of solid electrolytes have been investigated for their (a) superionic ion-conductivity (>10-4 S/cm), (b) mechanical softness and higher interfacial wettablity, (c) relatively simple synthesis and processing routes and (d) lower cost and earth abundance. Despite such advantages thiophosphates are known to have a narrow electrochemical stability window with a thermodynamical stability window between 1.7-2.6V (with respect to Li+/Li). Under such scenario, interfacial stability between Lithium thiophosphate/Li-metal and cathodes are primarily dictated by kinetic control by formation of a reaction passivation layer. Interfacial charge transfer depends on the detailed composition of the passivation reaction at the interface. The talk will highlight on the electrochemical performance characterization of the solid electrolyte, Li3PS4 and lithium-ion cathode such as LiFePO4. Detailed interfacial characterization between Li3PS4 and cathode interphases probed by XPS, NMR and electrochemical impedance spectroscopy (EIS) will be presented. In addition, synthesis and characterization of high capacity polysulfidophosphate cathodes based on catenation of sulfur to thiophosphate electrolytes, Li3(PS4)Sn where n = 5,8,6,3,2 will be discussed.

Understanding the lithium transport mechanism in Li9Cr3P8O29cathode material by molecular dynamics modeling

In this work, the atomistic simulation method based on Pedone model is applied to observe the concerted motion of lithium-ions in the perfect lattice of possible Li9Cr3(P2O7)3(PO4)2 cathode material. The simulation is carried out at a series of increasingly elevated temperatures in a super cell containing 27 unit cells. The superimposed Li+ trajectory at all timeframes offers an intuitive, reliable image of the Li+ migration in the crystal lattice. It reveals that lithium-ion propagates in a–b plane in an isotropic way and the propagation along the c axis is negligible. A typical lithium-ion migration path along the a or b axis can be described as migrating consecutively in the repeated sequence of Li1, Li3, Li1, and Li2. The energy barrier of Li9Cr3(P2O7)3(PO4)2 cathode material is about 0.345 eV and the estimated lithium-ion diffusion coefficients at room temperature are estimated at ca. 1.96 × 10−9 cm2 s−1. Compared with those intensively investigated cathode materials for lithium-ion batteries, which are normally considered to be highly potential or already in practical use, the lithium-ion conduction in the crystal grain for Li9Cr3(P2O7)3(PO4)2 cathode material is comparable or even superior. Therefore, the Li+ mobility is sufficiently high to exhibit good performances as a cathode material for lithium-ion batteries. More researches concerning the preparation, phase transformation, doping, surface modification, and the characterization of electro-chemical performance are urgently needed.

Synergistic effect of surface plane and particle sizes on the electrochemical performance of LiNi0.5Mn1.5O4 cathode material via a facile calcination process

A series of LiNi0.5Mn1.5O4 cathode samples with different morphologies was synthesized via a template method and facile post-calcination process. Rod-like and truncated octahedral particles with {111} surface are obtained through increasing the calcination temperature. The exposed surface of as-prepared materials is mainly detected by SEM and TEM images. Detailed characterization of electrochemical performance of samples reflects that the T-775 cathode sample displays superior rate capability, and the discharge capacity reaches 108.2 mAh g−1 at 100C. The energy density of full cells, T-775 sample as the cathode material and commercial graphite as the anode material, retain 534.9 Wh kg−1 after 100 cycles. These improvements might be due to the synergistic effect of the {111} surface and smaller particle sizes, which improves interfacial stability and reduces the diffusion distance of Li+ during the interaction/deinteraction process.

Sintering Temperature Induced Evolution of Microstructures and Enhanced Electrochemical Performances: Sol-Gel Derived LiFe(MoO4)2 Microcrystals as a Promising Anode Material for Lithium-Ion Batteries.

A facile sol-gel process was used for synthesis of LiFe(MoO4)2 microcrystals. The effects of sintering temperature on the microstructures and electrochemical performances of the as-synthesized samples were systematically investigated through XRD, SEM and electrochemical performance characterization. When sintered at 650°C, the obtained LiFe(MoO4)2 microcrystals show regular shape and uniform size distribution with mean size of 1–2 μm. At the lower temperature (600°C), the obtained LiFe(MoO4)2 microcrystals possess relative inferior crystallinity, irregular morphology and vague grain boundary. At the higher temperatures (680 and 700°C), the obtained LiFe(MoO4)2 microcrystals are larger and thicker particles. The electrochemical results demonstrate that the optimized LiFe(MoO4)2 microcrystals (650°C) can deliver a high discharge specific capacity of 925 mAh g−1 even at a current rate of 1 C (1,050 mA g−1) after 500 cycles. Our work can provide a good guidance for the controllable synthesis of other transition metal NASICON-type electrode materials.

An Electrochemical Performance Characterization Method for Comparing PEFCs of Varying Channel Dimensions

A method which allows for the comparison of polymer electrolyte fuel cell (PEFC) bipolar plates (BPs) with various channel dimensions is outlined here. It is applied to data from an experiment with different channel and land width and channel depth combinations for interdigitated and parallel designs. Channel and land width and channel depth varied from 0.25 mm to 1 mm on six different BP designs, and two stoichiometries were tested. Each condition was performed three times for repeatability. The method calculates the performance of each condition after accounting for reversible voltage and overpotential changes due to varying pressure and after eliminating ohmic resistance as a variable. In these data, the interdigitated flow field outperformed the parallel flow field. Designs are compared using the BP permeability as a benchmark metric. The method then calculates the area-specific ohmic resistance (ASR) of the cell. It was difficult to draw hard conclusions about changes in the ASR between flow field designs, but there may be more consistent liquid water removal from the gas diffusion layer (GDL) with smaller channel dimensions. It was found that concentration losses seem to be primarily a result of channel width, rather than channel depth.