Bound-bound transitions in hydrogenlike atoms induced by fast charged particles
Excitation cross sections for bound-bound transitions in optical levels in hydrogenlike atoms induced by fast charged particles
Omidvar, K.↗
SEARCH · Engineering Papers
Results for “Fast charge”
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Simultaneous neutron and X-ray tomography for visualization of graphite electrode degradation in fast-charged lithium-ion batteries
Advanced battery characterization using neutron and X-ray-based imaging modalities is crucial to reveal fundamental degradation modes of lithium-ion batteries (LIBs). Taking advantage of the sensitivity of neutrons to some low-Z (Li) and X-rays to high-Z materials (Cu), here we demonstrate the viability of simultaneous neutron and X-ray tomography (NeXT) as a non-destructive imaging platform for ex-situ 3D visualization of graphite electrode degradation following extreme fast charging (XFC). In addition, we underscore the benefits of the simultaneous of NeXT by combining the neutron and X-ray tomography data from the same sample location for material identification and segmentation of one pristine and two XFC-cycled graphite electrodes (9C charge for 450 cycles). Our ex-situ results and methodology development pave the way for the design of NeXT-friendly LIB geometries that will allow operando and/or in-situ 3D visualization of electrode degradation during XFC.
25 ENERGY STORAGE↗
Particle size effect of graphite anodes on performance of fast charging Li-ion batteries
Charging energy-dense lithium-ion batteries (LIBs) with thick graphite electrodes at high current densities are typically accompanied by poor performance and safety issues. The root cause is the onset of Li plating at the surface of graphite when lithiated to a high capacity within a short time period. Here, we investigated the behavior of graphite electrodes with various particle sizes under fast charge operations. Results from the electrochemical characterization on graphite electrodes exhibit the superiority of smaller particles over bigger particles in terms of suppressing the onset of Li plating and growth of plated Li particles. Observations from scanning electron microscopy also corroborate the presence of plated Li in electrodes with big graphite particles and its absence in graphite electrodes with small particles, when the cells were lithiated to 90% of the state of charge (SOC). Further, the improved performance of cells with the small particles might be associated with the low Li-ion concentration at the surface of graphite and thus reduced overpotential in graphite electrodes. The simulated results revealed that, compared to bigger particles, smaller particles have lower surface intercalation at any given cell SOC, which may significantly reduce the overpotential in the graphite electrodes and mitigate the onset of Li plating. This agrees well with experimental observations.
25 ENERGY STORAGE↗
Economic Storage Size Optimization for Electric Vehicle Extreme-Fast Charging Stations
En-route charging infrastructure for electric vehicles is critical to support transportation needs. These charging stations are likely to have high loads and especially sharp peak loads given fast charging capabilities needed to meet transportation schedules. In order to reduce both strain on distribution grid infrastructure and charging station operational costs, many stations are likely to employ behind the meter storage. This paper demonstrates a behind the meter storage sizing optimization that employs an open-source agent-based vehicle behavior model (BEAM) to determine the best sizing across many scenarios. This optimization and analysis is novel in that it examines how storage size impacts not only charging station cost and peak load, but also vehicle queue times. The optimization is also applied across a wide analysis region with sufficient diversity and numbers to provide novel statistical analysis of optimal sizes.
Aka, Julius↗
Phase Transformation Enables Stable Cycling and Fast Charging of Cation-Disordered Rocksalt Cathodes
Developing high-capacity, long-life cathodes is critical to overcome the energy limitations of current Li-ion batteries. In this work, we report a Li-excess cation-disordered rocksalt (DRX) cathode, Li 1.167 Mn0.7Ti 0.133 O 1.8 F 0.2 (M 0.7 F 0.2 ), which demonstrates excellent electrochemical performance. This cathode delivers a capacity approaching 250 mAh g –1 and maintains 200 mAh g –1 over 200 cycles with an average discharge voltage of 3.1 V at 2 V cutoff. The formation of a spinel-like phase during cycling enables fast charging, achieving over 240 mAh g –1 at 2C for 100 cycles. Combined X-ray absorption spectroscopy and transmission electron microscopy reveal reversible electrochemical redox processes and stable Mn local structures during 2 V discharge. These results highlight the potential of DRX cathodes for next-generation Li-ion batteries and provide insights into strategies to overcome kinetic limitations and optimize the cathode-electrolyte interface.
25 ENERGY STORAGE↗
Quantifying Graphite Solid-Electrolyte Interphase Chemistry and its Impact on Fast Charging
The solid-electrolyte interphase (SEI) enables the remarkable capacity retention of lithium-ion batteries, yet a comprehensive quantitative description of the SEI composition remains elusive. Using a combination of differential electrochemical mass spectrometry and mass spectrometry titration, we quantify graphite SEI components formed under electrolytes of varying salt concentrations. We find that, regardless of salt concentration, a conversion of initially deposited lithium ethylene dicarbonate to monocarbonates (likely lithium ethylene monocarbonate) and noncarbonate species occurs, and the extent of this conversion increases with electrolyte aging. Here, we additionally demonstrate that as the concentration increases (up to 2.0 M LiPF6), the SEI becomes progressively thinner with more LiF and less solid carbonates deposited. Finally, we reveal that less dead lithium formation and less solid carbonate deposition occur during prolonged fast charging for higher-concentration electrolytes. Because of the advantages imparted by a thinner SEI, the onset state of charge for lithium plating for the 2.0 M electrolyte is later than that predicted by a standard electrochemical model, underscoring the importance of explicit SEI effects in future electrochemical models.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Towards extreme fast charging of 4.6V LiCoO 2 via mitigating high-voltage kinetic hindrance
High-voltage LiCoO 2 (LCO) is an attractive cathode for ultra-high energy density lithium-ion batteries (LIBs) in the 3C markets. However, the sluggish lithium-ion diffusion at high voltage significantly hampers its rate capability. Herein, combining experiments with density functional theory (DFT) calculations, we demonstrate that the kinetic limitations can be mitigated by a facial Mg 2+ +Gd 3+ co-doping method. The as-prepared LCO shows significantly enhanced Li-ion diffusion mobility at high voltage, making more homogenous Li-ion de/intercalation at a high-rate charge/discharge process. The homogeneity enables the structural stability of LCO at a high-rate current density, inhibiting stress accumulation and irreversible phase transition. When used in combination with a Li metal anode, the doped LCO shows an extreme fast charging (XFC) capability, with a superior high capacity of 193.1 mAhg -1 even at the current density of 20C and high-rate capacity retention of 91.3% after 100 cycles at 5C. In conclusion, this work provides a new insight to prepare XFC high-voltage LCO cathode materials.
25 ENERGY STORAGE↗
Control, Fault Management, and Grid Support Functionality of an MV AC-DC Solid State Transformer based EV Extreme Fast Charging Station
Electric vehicles (EVs) have become increasingly popular in recent times while revolutionizing the consumer and commercial transportation market. The development of charging infrastructure has become one of the priorities for increasing the adoption of EVs. Extreme fast charging (XFC) technology can reduce the so-called ’range anxiety’ of consumers as they significantly reduce the charging time. With the advent of wide band-gap (WBG) power devices and improvement in power electronic converters, medium voltage (MV) solid state transformer (SST) based XFC system has the potential to replace the traditional XFC stations because of the lower footprint, ease of installation, enhanced control feature, and better system efficiency. The control system design is one of the critical aspects of the SST development process. Careful consideration and detailed analysis are required to find out suitable control method for the SST based on its topology among different centralized and decentralized control architectures. Also, the control parameters selection and potential improvement to the transient response of the controller ought to be investigated. Another major concern of the SST is different types of internal fault which reduces the overall reliability of the XFC system. As a result, designing a robust protection system is essential. Among different fault modes, open circuit switch faults have received significant attention as an active research area because of their likelihood and severe effects on converters. Therefore, the power stages used in the XFC system require functional and accurate open circuit switch fault management methods. An equally significant aspect of this SST based XFC is its compatibility in a microgrid where there is no synchronous generator present. When the grid is not available, the XFC SSTs can provide grid forming capability and continue supplying the critical loads in islanded mode. The transition between grid connected and islanded mode, especially the grid resynchronization process has to be carefully performed for the safety of the microgrid components. The challenges posed by the aforementioned issues have inspired the work done in this dissertation. Here, a 13.2 kV, 1 MVA, AC/DC SST for the XFC system is examined and a comparative analysis is conducted to select the control architecture based on feasibility of implementation and performance. A detailed control parameter design process is demonstrated considering the sensor dynamics and delay. The selected decentralized control method is augmented by introducing a novel sensor-less load current feedforward method to provide better voltage regulation at the DC bus during a change of load. Next, in the fault management section, a hierarchical failure mode effect analysis (FMEA) is proposed to enable a systematic design of the internal fault protection of the XFC SST as there are limited examples in the literature regarding the analysis of the safety and design of the protection of a power electronic converter system. Novel open circuit switch fault management methods for the converters in the system are presented. Finally, XFC SST based MV microgrid operations in grid connected mode and islanded mode are explored. A secondary control method for grid resynchronization is presented and a design process of control parameters is shown to ensure the stability of the secondary voltage and frequency regulation.
30 DIRECT ENERGY CONVERSION↗
Medium Voltage Solid State Transformer for Extreme Fast Charging Applications
A modular and scalable solid state transformer (SST) with direct medium voltage (MV) AC connectivity is proposed to enable DC extreme fast charging (XFC) of electric vehicles. Single-phase-modules (SPMs), each consisting of an active-front-end (AFE) stage and an isolated DC-DC stage, are connected in input-series-output-parallel (ISOP) configuration. The modular hardware is co-designed with decentralized control of the DC-DC stages where voltage and power balancing are achieved by each SPM using only its local sensor feedback; a centralized controller (CC) regulates the low voltage (LV) DC bus through the AFE stages without any sensor feedback form the SPMs. The controller architecture contrasts sharply with the prior art for MV AC to LV DC SSTs where high-speed bidirectional communication among SPMs and a CC are required for module-level voltage and power balancing, which severely limits the scalability and practical realization of higher voltage and higher power units. Detailed small-signal analysis and controller design guidelines are developed. Furthermore, a soft start-up strategy is presented. The proposed converter and control structure are validated through simulation and experimental results.
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
Interface chemistry informs about cathode and anode degradation during fast charging
Here, the aim of this study is to examine the development and makeup of the Solid Electrolyte Interphase (SEI) and Cathode Electrolyte Interphase (CEI) in lithium-ion batteries during rapid charging. Using X-ray photoelectron spectroscopy (XPS) and depth profiling, we investigate the chemical modifications occurring on the electrode surfaces during the initial formation and subsequent fast charge-discharge cycles. Our research shows that the anode's SEI initially comprises a thin layer rich in ketones, which then transforms into a thicker layer dominated by carbonaceous compounds during rapid charging cycles. Following assembly, lithium fluoride (LiF) quickly becomes a key element of the SEI, and its presence continues to grow substantially during the formation cycle, remaining the primary component throughout subsequent cycles. Initially, the cathode forms a thin oxide layer rich in ketones, with no noticeable carbonaceous CEI. The CEI primarily comprises LiF, which experiences an increase during the formation cycle and retains a thin layer of carbon coating after the initial rapid discharge. These findings show how the interphase layers impact the performance and stability of lithium-ion batteries, especially during fast charging for electric vertical take-off and landing (eVTOL) vehicles.
Fast charging↗
Suppressing strain propagation in ultrahigh-Ni cathodes during fast charging via epitaxial entropy-assisted coating
Surface reconstruction and the associated severe strain propagation have long been reported as the major cause of cathode failure during fast charging and long-term cycling. Despite tremendous attempts, no known strategies can simultaneously address the electro-chemomechanical instability without sacrificing energy and power density. Here we report an epitaxial entropy-assisted coating strategy for ultrahigh-Ni LiNi x Co y Mn 1-x-y O 2 (x ≥ 0.9) cathodes via an oriented attachment-driven reaction between Wadsley-Roth phase-based oxides and the layered-oxide cathodes. Further, the high anti-cracking and anti-corrosion tolerances as well as the fast ionic transport of the entropy-assisted surface effectively improved the fast charging/discharging capability, wide temperature tolerance and thermal stability of the ultrahigh-Ni cathodes. Comprehensive analysis from the primary and secondary particle level to the electrode level using multi-scale in situ synchrotron X-ray probes reveals greatly reduced lattice dislocations, anisotropic lattice strain and oxygen release as well as improved bulk/local structural stability, even when charging beyond the threshold state of charge (75%) of layered cathodes. Layered Ni-rich oxide cathodes are susceptible to challenges with surface reconstruction and strain propagation, limiting their cyclability. The authors propose a solution involving oriented attachment-driven reactions, utilizing Wadsley-Roth nanocrystals and layered oxide to induce an epitaxial entropy-assisted coating, effectively addressing these issues.
25 ENERGY STORAGE↗
Extreme fast charging of commercial Li-ion batteries via combined thermal switching and self-heating approaches
Abstract The mass adoption of electric vehicles is hindered by the inadequate extreme fast charging (XFC) performance (i.e., less than 15 min charging time to reach 80% state of charge) of commercial high-specific-energy (i.e., >200 Wh/kg) lithium-ion batteries (LIBs). Here, to enable the XFC of commercial LIBs, we propose the regulation of the battery’s self-generated heat via active thermal switching. We demonstrate that retaining the heat during XFC with the switch OFF boosts the cell’s kinetics while dissipating the heat after XFC with the switch ON reduces detrimental reactions in the battery. Without modifying cell materials or structures, the proposed XFC approach enables reliable battery operation by applying <15 min of charge and 1 h of discharge. These results are almost identical regarding operativity for the same battery type tested applying a 1 h of charge and 1 h of discharge, thus, meeting the XFC targets set by the United States Department of Energy. Finally, we also demonstrate the feasibility of integrating the XFC approach in a commercial battery thermal management system.
25 ENERGY STORAGE↗
Macro Analysis to Estimate Electric Vehicles Fast-Charging Infrastructure Requirements in Small Urban Areas
Electric vehicles (EVs) are known to reduce emissions and fossil fuel dependency. However, the limited range, long charging time, and inadequate charging infrastructure have hampered the adoption of EVs. The current EV charging infrastructure planning studies and tools require detailed information, extensive resources, and skills that can be a significant barrier to urban areas for finding the required charging infrastructure to support a targeted EV market share. This study generates regression models to estimate the number of direct current fast charging stations and the chargers to support the EV charging demand for urban areas. These models provide macro-level estimates of the required infrastructure investment in urban areas, which can be easily implemented by policy-makers and city planners. This study incorporates data obtained from applying a disaggregate optimization-based charger placement model, developed recently by the same authors, for multiple case studies to generate the required data to calibrate the macro-level models, in the state of Michigan. This simulated data set includes the number of charging stations and chargers for each market share, technology advancement scenario, and the transportation network topology. The results show that the number of charging stations reduces with battery size and charging power and increases with EV market share and the road network lane length. The number of chargers reduces with charging power, whereas it increases with battery size, EV market share, and vehicle miles traveled in the system. The model developed here can be applied to any state having urban characteristics and weather conditions similar to Michigan.
Engineering↗
Correlating wavelength dependence in LiMn2O4 cathode photo-accelerated fast charging with deformations in local structure
The growth in electrified transportation has benefited from the massive worldwide research efforts used to discover and improve electrode materials and electrolytes. Nevertheless, lithium-ion batteries still suffer from a slow-charging limitation. Recently, it has been demonstrated that white light illumination of LiMn2O4 provokes faster charging, improving the kinetics of delithiation without the use of nanostructured active materials. In this work, we probe the mechanism of photo-accelerated fast charging and show that Mn d-d electronic transitions occurring under red light illumination are largely responsible for the increased charging rate. It is further demonstrated through X-ray absorption spectroscopy methods that LiMn2O4 Mn-Mn bond distances shorten after d-electron excitation. The shrinkage in the crystal volume beneficially contributes to delithiation kinetics by lowering the resistance to lithium-ion conduction. Advanced materials that can absorb light to modulate their structure may provide us with a new mechanistic pathway to pursue for increasing charge transfer rates.
25 ENERGY STORAGE↗
Grid-Constrained Electric Vehicle Fast Charging Sites: Battery-Buffered Options
This case study summarizes recent Joint Office of Energy and Transportation technical assistance work performed by the National Renewable Energy Laboratory which involved helping a state department of transportation analyze the feasibility of a battery energy storage system solution at a grid-constrained EV charging location.
ADVANCED PROPULSION SYSTEMS↗
Intramolecular redox-site interplay effect on organic electrode for fast-charging and wide-temperature-range sodium-ion batteries
Organic electrode materials (OEMs) hold great promise for sodium-ion batteries (SIBs) due to their exceptional structural tunability and sustainability. However, the development of OEMs with fast redox kinetics and robust structural integrity remains challenging, especially over a wide temperature range. Herein, we propose an effective strategy to address both sluggish redox kinetics and insufficient structural stability in OEMs by constructing an intramolecular redox-site interplay effect. This effect is demonstrated by two hexaazatrinaphthylene-carboxylate isomers, namely HATN-m-COONa and HATN-o-COONa. Systematic experimental and computational results jointly reveal the intramolecular redox-site interplay effect in HATN-o-COONa decreases the rigid π-π stacking interactions and minimizes the skeleton structural distortion, offering faster redox kinetics and enhanced structural integrity in HATN-o-COONa compared to HATN-m-COONa (without intramolecular redox-site interplay effect). Consequently, HATN-o-COONa exhibits superior rate performance (258 mA h g−1 at 10 A g−1) and enhanced cycle stability (93% after 1000 cycles at 5 A g−1) compared to HATN-m-COONa. More importantly, HATN-o-COONa demonstrates exceptional wide-temperature adaptability, ranging from -40 °C (315 mA h g−1 at 0.1 A g−1) to 60 oC (343 mAh g-1 at 5 A g-1). This work establishes a promising design rationale for developing fast-charging and wide-temperature adaptable OEMs for energy storage systems.
Gao, Yawei [ORNL] (ORCID:0000000225672853)↗
Protection of Megawatt-Scale DC Fast Charging Infrastructure for Heavy-Duty Vehicles: Ultra-Fast DC Breaker Development, Testing, and Future Roadmap
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Rahman, Md Rakib-Ur↗
Ni-Rich Li[Ni x MnyCo 1– x – y ]O 2 Single Crystals as Superior Fast Charge Cathodes for Lithium-Ion Batteries
The utilization of single-crystal (SC) Li[Ni x MnyCo 1-x-y ]O 2 (NMC) cathodes has facilitated unparalleled performance in commercial high-energy lithium-ion batteries (LIBs). In the current study, we evaluate the application of SC cathodes in fast charge (FC)-LIBs where particle cracking is a predominant failure mechanism. Ni-rich SC-NMC samples with various compositions, sizes, and shapes are synthesized and investigated for their influence on FC performance. We reveal the necessity of utilizing smaller SCs (<1 μm) as larger sizes (>2 μm) experience significant particle-level lithium concentration gradients under FC conditions. To improve lithium transport and minimize side reactivities, we strategically expose the (104) crystal facets on the surface. Exceptional performance was observed on an optimized SC-LiNi 0.80 Mn 0.05 Co 0.15 O 2 , delivering a discharge capacity of 165 mAh/g even after 150 cycles at 6C charge. Our study not only demonstrates the promise of SC-NMC but also provides the key insights for the design and optimization of advanced cathodes for FC-LIBs.
25 ENERGY STORAGE↗