Active Material Cost Research Articles

Advancing Low-Cost Flow Battery Chemistries

Pumped-hydroelectric presently dominates U.S. grid electricity storage capacity resources, but the past decade has brought increasing levels of electrochemical energy storage (EES) installations.1 Policymakers have recognized the need for longer-duration systems as more EES gets added to the grid and sought systems that can provide durations of 8+ hours.2 , 3 Although Li-ion presently dominates EES deployments, the average duration of U.S. utility-based-systems are relatively short at 3 hours.4 Redox flow batteries (RFBs) have an advantage over Li-ion systems at long durations due to their system architecture. The marginal cost of another hour of RFB duration asymptotes to the cost of additional active materials and their storage containers, as opposed to the cost of additional Li-ion cells, packs, and modules.Leading vanadium RFBs have made cost reductions by improving the power density of their energy conversion stacks,5 , 6 but eventually are limited by the relatively high cost of their vanadium active materials. Vanadium RFB suppliers are actively seeking to reduce this cost through business innovations. Yet, from a technical perspective, switching to lower cost active materials can also permit economically feasible long duration RFB systems.7 RTX Technology Research Center has previously reported on the low cost active material chemistries including the sulfur/manganese (S-Mn) chemistry and ligand-coordinate metals (LCM, e.g. chromium/iron).8 , 9 S/Mn uses active materials based on low-cost sulfur, a waste product of fossil fuel production, and inexpensive manganese, an element presently used commercially in disposable primary cells. LCM chemistries use mass-produced organic ligands and inexpensive metal centers like iron, chromium, and titanium, and can rely on more neutral, and benign, electrolyte pH conditions that offer wider electrochemical stability windows. Along with these benefits, LCM chemistries bring new challenges such as managing pH in an environment where small absolute concentration changes have outsized effects. This abstract will focus on the progress made advancing low-cost chemistries toward industrial relevance via thousands of hours of operation and in full-sized cell/stack form-factors. Acknowledgements: The work presented herein was funded by the Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of Energy, under Award Number DE-AR000994. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. References Chalamala, B., DOE Global Energy Storage Database. Sandia National Laboratories: 2020.Padilla, M., Joint Long Duration Storage Request for Offers. Energy, S. V. C., Ed. Silicon Valley Clean Energy: 2020.Albertus, P.; Manser, J. S.; Litzelman, S., Long-Duration Electricity Storage Applications, Economics, and Technologies. Joule 2020, 4 (1), 21-32.Linga, V. Duration of utility-scale batteries depend on how they're used; EIA: U.S. EIA 'Today in Energy', March 25, 2022, 2022.Sun, C. N.; Mench, M. M.; Zawodzinski, T. A., High Performance Redox Flow Batteries: An Analysis of the Upper Performance Limits of Flow Batteries Using Non-aqueous Solvents. Electrochimica Acta 2017, 237, 199-206.Perry, M. L.; Darling, R. M.; Zaffou, R., High Power Density Redox Flow Battery Cells. ECS Transactions 2013, 53 (7), 7-16.Wadia, C.; Albertus, P.; Srinivasan, V., Resource constraints on the battery energy storage potential for grid and transportation applications. Journal of Power Sources 2011, 196 (3), 1593-1598.Yang, Z.; Gerhardt, M. R.; Fortin, M.; Shovlin, C.; Weber, A. Z.; Perry, M. L.; Darling, R. M.; Saraidaridis, J. D., Polysulfide-Permanganate Flow Battery Using Abundant Active Materials. Journal of The Electrochemical Society 2021, 168 (7), 070516.Saraidaridis, J.; Yang, Z., Electrolyte Takeover Strategy for Performance Recovery in Polysulfide-Permanganate Flow Batteries. Journal of The Electrochemical Society 2021, 168 (11), 110556.

High-Rate and Durable Zinc-Based Flow Batteries for Large-Scale Energy Storage

Large-scale energy storage is a key enabling technology for the widespread adoption of renewable energy such as wind and solar power. Among various technologies, zinc-based flow batteries stand out as one of the most promising candidates due to the high energy density, low cost, and use of earth-abundant active materials. However, the low operating current density and short cycle life resulting from notorious zinc dendrite formation, large internal resistance, and sluggish reaction kinetics pose a great challenge for their practical applications. Although great efforts have been made to address these issues, previous works mainly focused on one specific aspect, making it challenging to boost the overall performance of zinc-based flow batteries. In this presentation, a systematic study on the effects of key components on the electrochemical performance of zinc-bromine flow batteries will be presented. Our results show that all key components (electrodes, electrolytes, membranes, and flow fields) can exert a significant influence on the electrochemical performance. More impressively, a high areal capacity of >200 mAh/cm2 and an operating current density of as high as 400 mA/cm2 can be achieved by optimizing the design and operating parameters. Underlying mechanisms and perspectives for further improvement will be discussed during the presentation.

An innovative approach to design readily synthesizable polymers for all-polymer solar cells

The communalization of all-polymer solar cells depends on the cost of active layer materials. We have introduced a framework to find the easily synthesizable polymers. Breaking Retrosynthetically Interesting Chemical Substructures (BRICS) method is used to generate a large database of polymers and synthetic accessibility of generated polymers is predicted. The generated database is visualized using various methods. Energy levels of polymers are also predicted using pretrained machine learning models. Polymers are screened on the basis of predicted properties. Library of polymers are displayed using the T-distributed Stochastic Neighbor Embedding (t-SNE) visualization. Structure Activity Landscape Index (SALI) visualization is also used. A significant change is observed in synthetic accessibility score on structural changes. The histagradient boosting regressor is used to predict the energy levels of polymers that energy levels play significant role in the selection of materials for organic photovoltaic cells. Synthetic accessibility of polymers is analyzed and a significant number of polymers are easy to synthesize. Thirty polymers are selected through screening process that are potential candidates for organic photovoltaic cells.

Comparative analysis of a mining truck motor with permanent magnets in a rotor and a synchronous homopolar motor without magnets in a drive

The relevance. Increasing need for using mining trucks with a diesel-electric (hybrid) drive for development of minerals. Improving operational and cost characteristics of the electric drive of mining trucks helps to reduce costs in the development of minerals. The main aim. To compare theoretically the performance of synchronous traction motors of various designs (a conventional design with permanent magnets inside a rotor and a homopolar design without permanent magnets with an excitation winding on a stator), optimized by the same method, in the drive of a mining truck. To optimize the motor design to reduce power loss and required inverter power, as well as to limit torque ripple and reduce the risk of permanent magnet demagnetization. Objects. Design of twelve-pole nine-phase synchronous AC motors with a rated power of 370 kW of various designs: a homopolar motor without permanent magnets with an excitation winding on the stator and a motor of a traditional design with permanent magnets in the rotor. Methods. Derivative-free optimization method; equivalent circuit method; mathematical modeling; two-dimensional finite element method. Results. Based on the analysis, the advantages and disadvantages of the considered motors were revealed. The advantage of the motor with permanent magnets in the rotor is reduction in active part length by 30 %. The advantage of the homopolar motor with an excitation winding on the stator are 4.6 times lower cost of active materials. In addition, the homopolar motor has a more reliable design, without the risk of overheating, demagnetization or deterioration of the properties of permanent magnets over time

Quantifying the Open-Circuit Voltage (OCV) Hysteresis in Ternary Li-Rich Mn-Ni Layered Oxides

To achieve the high energy densities needed for automotive applications while keeping the cathode active material (CAM) cost as low as possible, lithium- and manganese-rich NCMs (LMR-NCMs), e. g., Li1.14(Ni0.26Co0.14Mn0.60)0.86O2, are considered as possible candidates. Furthermore, in the past years there was a tendency for replacing expensive and supply-limited cobalt from cathode active materials, resulting in cobalt-free LMR-NMs with the general composition x Li2MnO3 · (1-x) LiMO2 (M = Ni, Mn; 0.33 ≤ x ≤ 0.5) or alternatively expressed as Li1+δ[NiyMnz]1-δO2(y+z= 1, 0.14 ≤ δ ≤ 0.20).1 Even though these materials are able to reversibly provide capacities of ≈ 250 mAh/g, there are numerous challenges to overcome, like extensive gas evolution, capacity and voltage fading over extended charge/discharge cycling, and the substantial open-circuit voltage (OCV) hysteresis, which hamper the implementation of LMR-NCMs in the automotive sector.2–5 It was shown in previous publications that the OCV hysteresis, an intrinsic property of LMR-NCMs, significantly lowers the charge/discharge energy efficiency and thus increases heat generation.2, 6, 7 Furthermore, it was qualitatively shown that the voltage fading as well as the OCV hysteresis is dependent on x in x Li2MnO3 · (1-x) LiMO2 (M = Ni, Mn, Co).5, 6 In order to investigate the relation between composition and OCV hysteresis for Co-free overlithiated layered oxides, we synthesized CAMs with various compositions with the general formula x Li2MnO3 · (1-x) LiMO2 (M = Ni, Mn; 0.33 ≤ x ≤ 0.5), proving the presence of the layered structure of the materials with Rietveld refinements on the collected X-ray diffraction data. The OCV hysteresis of the synthesized and electrochemically activated LMR-NMs is determined from slow charge/discharge cycles with intermittent OCV holds. Based on these data, the OCV hysteresis of LMR-NMs can be correlated with their specific composition. References D. Andre, S.-J. Kim, P. Lamp, S. F. Lux, F. Maglia, O. Paschos and B. Stiaszny, J. Mater. Chem. A, 3(13), 6709–6732 (2015). L. Kraft, T. Zünd, D. Schreiner, R. Wilhelm, F. J. Günter, G. Reinhart, H. A. Gasteiger and A. Jossen, J. Electrochem. Soc., 168(2), 20537 (2021). J. R. Croy, M. Balasubramanian, K. G. Gallagher and A. K. Burrell, Accounts of chemical research, 48(11), 2813–2821 (2015). T. Teufl, B. Strehle, P. Müller, H. A. Gasteiger and M. A. Mendez, J. Electrochem. Soc., 165(11), A2718-A2731 (2018). J. R. Croy, K. G. Gallagher, M. Balasubramanian, B. R. Long and M. M. Thackeray, J. Electrochem. Soc., 161(3), A318-A325 (2014). F. Friedrich, S. Pieper and H. A. Gasteiger, J. Electrochem. Soc., 168(12), 120502 (2021). B. Strehle, T. Zünd, S. Sicolo, A. Kiessling, V. Baran and H. A. Gasteiger, J. Electrochem. Soc., 169(2), 20554 (2022). Acknowledgement This work is financially supported by the BASF SE Network on Electrochemistry and Battery Research.

Multifaceted Effects of Ring Fusion in Charged Dialkoxyarene Redoxmers

Redox flow batteries (RFBs) hold promises for long-duration energy storage, with various chemistries demonstrated by academia and industry. However, their practical applications remain limited due to high active material cost, low energy density, narrow voltage window, and limited cyclability. Improving the performance of redox active materials (redoxmers) in RFBs is crucial for addressing these challenges. In this study, to better understand the impact of π-conjugation of aromatic redox cores on the redoxmers’ electrochemical behavior, we systematically investigated a series of dialkoxy benzene based redoxmers, including 1,4-dimethoxy benzene (DMB), 1,4-dimethoxynaphthalene (DMN), 2-ethyl-9,10-dimethoxyanthracene (EDMA). As the conjugation increases from DMB to DMN, we observed a lower redox potential, improved kinetic stability, and longer cycling life. However, further expanding the conjugation as in EDMA resulted in rapid O-dealkylation of the radical cation, possibly due to increased strain in methoxy groups. For DMN, the radical cation is observed to be prone to neutralization (likely via disproportionation) and can be recharged, suggesting a longer cycling life than the calendar life. Our study indicates that extending the π-system alters reactivity in multiple ways, and lowering the oxidation potential through π-conjugation to improve redoxmer stability should be cautiously pursued.

Study of a Spoke-Type Ferrite Structure as an Alternative to Surface-Mounted NdFeB PMSGs: A Performance Comparison Based on Getting the Same Efficiency

A spoke-type permanent magnet synchronous generator (PMSG) with ferrite magnets that could be an alternative to a PMSG with 2 kW, 20-poles, surface-mounted NdFeB magnets with the same power, the number of poles and efficiency value was designed in this study. The designs obtained by the finite element analysis were compared in terms of size, magnet properties, flux distributions, cogging torque, induced voltages, total harmonic distortion, and active material costs. The amount of magnet used in the ferrite magnet generator was approximately 2.7 times that of N38 to obtain the same power. While the active volume (D2L) of the ferrite magnet generator was obtained as approximately twice that of a surface-mounted neodymium magnet, the total generator cost was 1.45 times less in the ferrite magnet structure. When evaluated in terms of their performance, the cogging torques were obtained at approximately the same value, and the voltage harmonics were obtained at lower values in the spoke-type generator.

Interfacial Contact Management in Perovskite Solar Cells with Carbon Top Electrode

Perovskite solar cells (PSCs) represent a promising photovoltaic technology that has great potential for mass application. The main advantages of the perovskite solar cells are related to simplicity of their fabrication, tunable optical properties, and low cost of active materials. For further reducing the device costs, graphite‐based contacts are often used to replace an energy‐inefficient deposition of metal contacts, which is a trade‐off between the cost and power conversion efficiency (PCE) of devices. Herein, a new approach to increase the PCE of hole transport layer‐free perovskite cells with carbon‐based electrodes by the sequential treatment of the perovskite absorber layer and perovskite/carbon electrode interface with methylammonium iodide is presented. The proposed passivation technique leads to a dramatic improvement in the device power conversion efficiency from the initial 3.9% to 7.9%. The origin of the enhanced device performance is attributed to the passivation of defects on the perovskite/carbon interface and, most importantly, improving the electrical contact between the top electrode and absorber layer.

Comparative Study of Electrically Excited Conventional and Homopolar Synchronous Motors for the Traction Drive of a Mining Dump Truck Operating in a Wide Speed Range in Field-Weakening Region

A synchronous homopolar motor (SHM) has a salient pole passive rotor, an excitation winding located on the stator, and no permanent magnets, which ensures high reliability and makes this type of motor a good alternative to motors traditionally used in traction drives. However, there is no comparison between SHMs and conventional brushed synchronous machines for traction applications in the literature. In this paper, the performances of a wound rotor synchronous machine (WRSM) and SHM are theoretically compared at the operating points of a 370 kW dump mining truck drive traction curve that has a 10:1 constant power range in the field weakening region. The nine-phase motors under comparison have the same outer diameter of the stator lamination. Before comparison, both motor designs are optimized using the Nelder–Mead method to minimize the semiconductor inverter rated current and the operating cycle power loss. The main advantages of the WRSM, which was designed, are reduction in stator length, smaller losses, and smaller inverter. The reduction in the total stator length was by 1.23 times taking into account the winding end parts as well. Losses were reduced by 1.21 times for the same radius of the stator lamination. Finally, the cost of power modules of the inverter was decreased by 1.4 times. SHM is more reliable since its rotor does not have an excitation winding and a diode rectifier, as in a WRSM with a brushless exciter. In addition, SHM provides lower consumption of copper, which reduces the total mass and cost of active materials. This article also introduces a new term, “inverter utilization factor”, which can be useful, more informative than motor power factor, when comparing traction drives with different types of motors.

Understanding Capacity Fade in Organic Redox-Flow Batteries Using Uncertainty Quantification Techniques and Zero-Dimensional Modeling

We introduce the use of Bayesian uncertainty quantification to provide data-informed assessments of the probability of different hypotheses of reactant decay, and to estimate reactant decay parameters from experimental data with quantified uncertainty. As a case study, we use these techniques to extract rate constants describing the nucleophilic attack of quinone-based RFB reactants by water, as measured using in operando ultraviolet-visible spectrophotometry. We then introduce a zero-dimensional electrochemical flow cell model3 which can simulate capacity fade given a reactant decay mechanism and associated parameters, and the cycling protocol. This work has the potential to shed light on the relationship between capacity fade and reactant decay in various organic RFB chemistries, and to enable prediction of the lifetimes of commercial-scale RFBs.(1) Brushett, F. R.; Aziz, M. J.; Rodby, K. E. On Lifetime and Cost of Redox-Active Organics for Aqueous Flow Batteries. ACS Energy Letters 2020, 879-884. DOI: 10.1021/acsenergylett.0c00140. Dieterich, V.; Milshtein, J.; Barton, J.; Carney, T.; Darling, R.; Brushett, F. Estimating the Cost of Organic Battery Active Materials: A Case Study on Anthraquinone Disulfonic Acid. Translational Materials Research 2018.(2) Kwabi, D. G.; Ji, Y.; Aziz, M. J. Electrolyte Lifetime in Aqueous Organic Redox Flow Batteries: A Critical Review. Chemical Reviews 2020.(3) Modak, S.; Kwabi, D. G. A Zero-Dimensional Model for Electrochemical Behavior and Capacity Retention in Organic Flow Cells. Journal of The Electrochemical Society 2021, 168 (8), 080528. DOI: 10.1149/1945-7111/ac1c1f.

High Energy and Low-Cost Membrane-Free Chlorine Flow Battery

Grid-scale energy storage is essential for reliable electricity transmission and renewable energy integration. Redox flow batteries (RFB) provide affordable and scalable strategies for stationary energy storage. But most of the current RFB chemistries are based on expensive transition metal ions or synthetic organics. Here, we report a reversible Cl2/Cl- redox flow battery through electrolysis of aqueous NaCl electrolyte, the as-produced Cl2 is stored and extracted using carbon tetrachloride (CCl4) or mineral spirit flow. The immiscibility between the CCl4 and NaCl electrolyte enables a membrane-free design with energy efficiency of >91 % and energy density of 125.7 Wh/L. With the inherently low cost of active materials (~5 $/kWh) and highly reversible redox reaction of Cl2/Cl-, the chlorine flow battery leaves significant space to meet the stringent price and reliability target for stationary energy storage. Figure 1

(Invited) A Micelle Electrolyte Enabled By Fluorinated Ether Additives for Polysulfide Suppression, High Voltage Cathode, and Li Metal Anode Stabilization

The Li-S battery is a promising next-generation technology due to its high theoretical energy density (2600 Wh/kg) and low active material cost. However, poor cycling stability and coulombic efficiency caused by polysulfide dissolution have proven to be major obstacles for a practical Li-S battery implementation. In this work, we develop a novel strategy to suppress polysulfide dissolution using hydrofluoroethers (HFEs) with bi-functional, amphiphlic surfactant-like design: a polar lithiophilic “head” attached to a fluorinated lithiophobic “tail.” A unique solvation mechanism is proposed for these solvents whereby dissociated lithium ions are readily coordinated with lithiophilic “head” to induce self-assembly into micelle-like complex structures. Complex formation is verified experimentally by changing the additive structure and concentration using small angle X-ray and neutron scattering. These HFE-based electrolytes are found to prevent polysulfide dissolution and to have excellent chemical compatibility with lithium metal: Li||Cu stripping/plating tests reveal high coulombic efficiency (>99.5%), modest polarization, and smooth surface morphology of the uniformly deposited lithium. Li-S cells are demonstrated with 1395 mAh/g initial capacity and 71.9% retention over 100 cycles at >99.5% efficiency—evidence that the micelle structure of the amphiphilic additives in HFEs can prohibit polysulfide dissolution while enabling facile Li+ transport and anode passivation. In addition, this type of electrolytes is also stable toward high voltage cathode to enable a lithium metal anode and high voltage cathode high-energy density rechargeable lithium battery.

Comparison of Interior Permanent Magnet and Synchronous Homopolar Motors for a Mining Dump Truck Traction Drive Operated in Wide Constant Power Speed Range

Synchronous homopolar motors (SHMs) with an excitation winding located at the stator and a toothed salient pole rotor are a good alternative to motors traditionally used in traction applications such as induction motors or interior permanent magnet synchronous motors (IPMSM). This study presents the results of a theoretical comparison between an IPMSM and an SHM in a traction application with a constant power speed range of 1:10, which is specific to the mining truck drives, and with a rated power of 370 kW. The considered IPMSM and SHM have the same number of phases, poles and stator slots, and the same outer diameter of the stator lamination. The IPMSM design is optimized using the Nelder–Mead method. The main objectives of optimization are to minimize the average losses in the operating cycle and to limit the required power of the semiconductor inverter. The performance of the optimized IPMSM is compared with the previously obtained performance of the SHM optimized by the same method. Although the average losses in the operating cycle in the compared motors are approximately equal, the losses at high speed for the IPMSM are about two times greater than at low speed with maximum torque, which means that there is a need to intensify the IPMSM cooling system and there is deterioration of reliability. The advantage of the IPMSM is the reduction in the length of the active part by 30%. The advantage of the SHM is that there is 4.6 times lower cost of active materials. In addition, the SHM is more reliable than the IPMSM, as there is no risk of overheating, demagnetization or degradation of permanent magnets over time.

A multifunctional nano filler for solid polymer electrolyte toward stable cycling for lithium-metal anodes in lithium–sulfur batteries

Lithium–sulfur (Li–S) batteries are considered as very promising energy storage systems due to their higher theoretical performance and lower active material cost. However, the notorious shuttle effect and lithium dendrite growth have severely restricted the industrial production of Li–S batteries. In this study, we used polyethylene oxide (PEO) as the matrix and added multifunctional nanofillers (nano In2O3) to effectively inhibit the shuttle effect caused by the dissolution of lithium polysulphides (LiPSs) in Li–S batteries. As a multifunctional filler, nano-In2O3 not only improves the ionic conductivity of the PEO electrolyte, but also forms a Li–In alloy layer in situ at the polymer/anode interface, which can cause the rapid diffusion of lithium ions and prevent the side reactions between lithium metal anode and the electrolyte. Achieving the effect of stabilizing the lithium metal anode and suppressing the shuttle effect. Multiple problems in the system are solved by introducing a single component with multiple functions. The symmetrical lithium battery based on the PEO/LiTFSI/In2O3 solid polymer electrolyte (PEO/LiTFSI/In2O3 SPE) has higher cycle stability (over 1200 h) because it is more stable to the lithium metal anode. The Li–S full battery also exhibits excellent electrochemical performance. After 500 cycles at 1C, its capacity can be maintained at 570 mAh g−1, the capacity decay rate is 0.038%. The coulombic efficiency (CE) during the cycle is also close 100%.

Comparative Design and Performance Analysis of 10 kW Rare-Earth and Non-Rare Earth Flux Reversal Wind Generators

Generators are a key technological element of the wind energy generation system. Currently, there is an increasing interest in adopting non-conventional stator-mounted permanent magnet generators, e.g., flux reversal generators (FRGs), which is a good alternative to conventional synchronous generators for medium-speed wind turbine generator applications. The usage of FRG with rare-earth (RE) permanent magnets (PMs) is increasing due to their high efficiency and high power density factors. However, RE PMs are unattractive to wind generators in terms of their cost and unpredictable market supply. In this paper, an attempt is made to study the potential of FRG with non-rare earths (ferrite PMs) for wind generators. The three-phase, 6/8 pole FRG is designed and compared with RE and NRE PMs for wind generator application at 375 r/min, 10 kW. Using 2D FEA, both the generators are compared in terms of their power generating performance with excellent overload capability. It shows that the average efficiency of the generators is approximately similar, but the torque density of NRE-FRG is only 51% that of RE-FRG. The NRE-FRG design is heavier, with the total active mass being 2.6 times higher than the RE-FRG, but with the estimated total active material cost of both generators almost the same. Moreover, the toque ripple for RE-FRG is 64% higher than for NRE-FRG. The demagnetization risk analysis was performed, and it is found that at higher temperatures, RE-FRG structures are prone to higher demagnetization risks, while it is much lower in NRE-FRGs. In summary, it is found that NRE-FRG is a suitable alternative to RE-FRG for medium-speed wind turbine generator applications in the 10-kW power range.

Electrolyte Takeover Strategy for Performance Recovery in Polysulfide-Permanganate Flow Batteries

The abundance of active material precursors for a polysulfide-permanganate flow battery makes it a compelling chemistry for large-scale, and potentially long-duration (>10 h), grid electricity storage. Precipitation, arising from either reactant crossover or electrolyte side reactions, decrease cell efficiencies during charge/discharge cycling. Regardless of the abundance and low cost of active materials, a system without high cyclability cannot meet grid electricity storage economic targets for applications that cycle regularly. Precipitated species can be removed, and reactor efficiency performance restored, by using an electrolyte takeover process, or ETP. Two ETP methods are investigated. One ETP uses the negative electrolyte, an alkaline polysulfide (pS) solution, as takeover solution, and another uses dilute acidic peroxide (DAP) as the takeover solution. Both ETPs maintain functional cell operation within an acceptable performance range over >1000 h and >200 cycles, a duration over which cells that do not undergo ETPs clog and fail. The DAP ETP proves especially effective and limits irrecoverable voltage efficiency fade below 0.02%/cycle. These ETPs, either individually, or in combination, can enable the requisite cyclability for practical polysulfide-permanganate flow battery systems.

Is Aluminum Useful in Ni-Rich Li-Ni-Mn-O Positive Electrode Materials for Lithium-Ion Batteries?

The low cost and high specific capacity of Ni-rich cathode active materials have made them promising materials for affordable, high performance Li-ion batteries. However, increasing the Ni-content in the cathode results in lower cycling performance and lower thermal stability.1 Meanwhile, lithium nickel manganese oxides (Li-Ni-Mn-O) are also inexpensive materials that benefit from high thermal stability and high energy density due to their high operation potential.2 Although manganese improves the performance of Ni-based materials, it also enables more cation mixing and reduces the rate capability of the cathodeAl-doping of cathode materials, although it lowers the initial capacity of the cell, has shown to reduce changes in the lattice of the material during delithiation resulting in improved cycling stability. The presence of Al in the lattice also decreases the charge-transfer resistance by facilitating Li-diffusion.3 Although the presence of Al has proved its virtue in commercial cathode materials such as LiNixCoyAl1-x-yO2 (NCA) and LiNixMnyCozAl1-x-y-zO2 (NMCA) it has yet to be used commercially in Co-free systems. In this work, Li(NixMn1-x)O2 (NM) systems of 3 different particle sizes (3.5 μm, 13 μm and 16 μm) as well as their Al-doped counterparts, Li(NixMn1-x-yAly)O2 (NMA), were studied. Figure 1 shows that the array of layered materials used in this study were optimally synthesized to be stoichiometric, single-phase materials with minimal cation mixing. Half cells and full cells were then constructed to evaluate the effect of Al on cycling stability, Li diffusion measurements were made to study rate capability and accelerated rate calorimetry was used to compare thermal stability. This head-to-head comparison of Li-Ni-Mn-systems with and without Al dopant will determine the effectiveness of Al in Ni-rich, Co-free cathode materials.References Li, H. et al. An Unavoidable Challenge for Ni-Rich Positive Electrode Materials for Lithium-Ion Batteries. (2019) doi: 10.1021/acs.chemmater.9b02372 Dou, S. Review and prospect of layered lithium nickel manganese oxide as cathode materials for Li-ion batteries. 911–926 (2013) doi.org/10.1007/s10008-012-1977-z Wang, G. X., Zhong, S., Bradhurst, D. H., Dou, S. X. & Liu, H. K. LiAlδNi1-δO2 solid solutions as cathodic materials for rechargeable lithium batteries. Solid State Ionics 116, 271–277 (1999). doi.org/10.1016/S0167-2738(98)00351-8 Figure 1

Design of a direct current motor with a windingless rotor for electric vehicles

Modern electric vehicles typically exploit synchronous motors with magnetoelectric excitation as traction engines. While possessing a series of undeniable advantages, the synchronous motor has one significant drawback ‒ the high cost predetermined by the high price of permanent magnets. In addition, the impossibility to disable a magnetic field in case of engine malfunction can lead to an emergency on the road. Given this, there is a need to design new structures of electrical machines with electromagnetic excitation. The structure of a DC traction motor with electromagnetic excitation involving the rotor or stator segmentation makes it possible to considerably weaken the field of the armature transverse reaction by decreasing magnetic conductivity of the magnetic circuit in the transverse direction. Therefore, such a structure lacks commutating poles and a compensation winding. There are no permanent magnets in the structure, all windings are stationary, an electronic switch is used instead of a collector, and a windingless low-inertia rotor does not require additional measures to remove heat. That all has made it possible to significantly reduce the cost of active materials for the traction engine and improve its reliability. To test the performance of the new design, a full-size model of the engine and a working experimental prototype were fabricated. Applying a synchronous jet engine with magnetization for the BMW i3 electric car as an analog, the engine calculations were performed and its simulation was carried out. The results of the analysis show that the mass of the new engine is 35 % greater than the mass of the analog but the cost of active materials is less than that of the analog by 63 %. The results testify to the possibility of implementing a given structure industrially

Highly sensitive piezoresistive pressure sensors based on laser-induced graphene with molybdenum disulfide nanoparticles

Wearable pressure sensors have drawn significant attention because of their extensive applications in motion detection, tactile sensing, and health monitoring. However, the complex manufacturing process and high cost of active materials make low-cost, large-scale production elusive. In this work, we report a flexible piezoresistive pressure sensor assembled with two 3D laser-induced graphene (LIG) foam electrodes on a polyimide thin film from a simple laser scribing process in the ambient environment. The design of the air gap between the two foam electrodes allows the sensor to showcase a low limit of detection of 0.274 Pa, which provides favorable sensing performance in motion detection and wrist pulse monitoring. The addition of spherical MoS2 nanoparticles between the two foam electrodes further enhances the sensitivity to 88 kPa−1 and increases the sensing range to significantly outperform the previous literature reports. The demonstrated LIG pressure sensors also exhibit fast response/recovery rates and excellent durability/repeatability.

Integrated Optimal Design of Permanent Magnet Synchronous Generator for Smart Wind Turbine Using Genetic Algorithm

In recent years, the investment in the wind energy sector has increased in the context of producing green electricity and saving the environment. The installation of small wind turbines (SWTs) represents an actual strategy for meeting energy needs for off-grid systems and certain specialized applications. SWTs are more expensive per kilowatt installed as compared to large-scale wind turbines. Therefore, the main objective of this study is to produce an economical technology for the wind power market offering low-cost SWTs. The idea consists of considering a simple structure of the wind turbine using direct-drive permanent magnet synchronous generator (DDPMSG). DDPMSGs are the most useful machines in the wind energy field thanks to several advantages, such as elimination of noise and maintenance cost due to suppression of the gearbox and absence of the rotor circuit excitation barriers by the presence of the permanent magnets (PMs). Their major downside is the high cost of active materials, especially the PMs. Thus, the improvement of the generator design is treated as being the main component of the considered chain to assure active materials’ mass and cost reduction. The methodology studied aims to explain the approach of the design integrated by optimization of the considered system. It is based on the elaboration of analytical models to find a feasible structure for the system, taking into account the multi-disciplinary analysis. The relevance of these models is validated by the finite element method using 2D MATLAB-FEMM simulation. The models are integrated to elaborate the optimization problem based on a genetic algorithm to improve the cost of the proposed generator by minimizing the mass of its active constructive materials. As an outcome, an optimal solution is offered for the wind generators market, providing a 16% cost reduction.