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BATPAC--VERSION 5.0
Argonne National Laboratory has worked on electrochemical energy storage for several decades. The focus on lithium-ion chemistries started in the early 1990s, developing new materials, synthesis methods, and performance characterizations. Sponsored by the U.S. Department of Energy, Energy Efficiency and Renewable Energy, Vehicle Technologies Office (DOE-EERE-VTO), Argonne has led with many advances. The experimental activities were complemented with multi-scale modeling that ranged from the atomic to the system (manufacturing processes and automobiles) level. The Battery Performance and Cost (BatPaC) model is a calculation method based on Microsoft¿ Office Excel spreadsheets that have been developed at Argonne for estimating the performance and manufacturing cost of lithium-ion batteries for electric-drive vehicles including hybrid-electrics (HEV), plug-in hybrids (PHEV) and pure electrics. The effort is being funded by the Vehicle Technology Office (VTO), which is part of the Energy Efficiency and Renewable Energy (EERE) office of the U.S. Department of Energy (USDOE). BatPaC was first developed in 2007, was subsequently peer-reviewed, and it has served Argonne researchers and the greater battery community in studying the impact of material properties on performance at the pack level. With further developments, the model now allows the design of cells and battery packs for automotive applications, to meet performance requirements (power, energy, recharge time), and estimates the cost of manufacturing the designed batteries. Since the cost depends on the materials he design, and the manufacturing process, this bottom-up model/tool enables the user to study their effects. Designed or the lithium-ion cell and battery researcher, BatPaC helps answer many questions by being 1.Transparent in the assumptions made and the method of calculation 2.Capable of designing a battery specifically for the requirements of an application 3.Constrained by the physical limitations that govern battery performance 4. A bottom-up calculation approach to account for every cost factors. BatPaC predicts the impact of promising materials (and their properties) on the performance metrics relevant for the different applications. Researchers can use the specific capacities and the half-cell voltages of a particular set of electrode materials to calculate the mass and volume of a cell to develop a model incorporating the properties of all the other materials in the cell and the design of the cell enclosure. These calculations not only reveal the impact of an improved material but also enable researchers to calculate the material properties that would be needed to meet the performance criteria of a full battery pack. With this information, researchers can provide he battery industry with realistic expectations that will help it more successfully advance novel battery technologies an Applications.
Probing the Role of Multi-scale Heterogeneity in Graphite Electrodes for Extreme Fast Charging
Electrode-scale heterogeneity can combine with complex electrochemical interactions to impede lithium-ion battery performance, particularly during fast charging. This research investigates the influence of electrode heterogeneity at different scales on the lithium-ion battery electrochemical performance under operational extremes. We employ image-based mesoscale simulation in conjunction with a three-dimensional electrochemical model to predict performance variability in 14 graphite electrode X-ray computed tomography data sets. Our analysis reveals that the tortuous anisotropy stemming from the variable particle morphology has a dominating influence on the overall cell performance. Cells with platelet morphology achieve lower capacity, higher heat generation rates, and severe plating under extreme fast charge conditions. On the contrary, the heterogeneity due to the active material clustering alone has minimal impact. Our work suggests that manufacturing electrodes with more homogeneous and isotropic particle morphology will improve electrochemical performance and improve safety, enabling electromobility.
Deconvoluting Effects of Lithium Morphology and SEI Stability at Moderate Current Density Using Interface Engineering
Lithium (Li)-morphology and solid electrolyte interphase (SEI) are among the most significant performance regulators in Li-metal batteries (LMBs). While both Li-morphology and SEI composition play key roles in the cyclability of LMBs, less is understood about the individual contributions of each factor to overall Li reversibility, particularly at a practical current density (1 mA cm −2 ) at which the kinetics of both factors are not naturally separated. Herein, an interface engineering approach is introduced to deconvolute the impacts of Li-morphology and SEI composition on battery performance. By using interfacial nanofilms with differing resistivity (resistive HfO 2 versus conductive ZnO), the morphology of Li is varied, and by virtue of similar acidic character of the nanofilms, the formation of anion-rich SEIs is maintained. It is established that although the surface acidity of the thin films enables preformation of a more anion-rich SEI, it is not preserved after Li plating. It is further shown that resistance-controlled, low-surface-area Li-morphology exhibits up to threefold increase in stable cycle life when tested in multiple electrolytes. Overall, these findings explain why Li-morphological control is more advantageous for performance improvement than preformed SEI modulation due to the inherent challenges in SEI preservation.
Transforming nanoscale VO 2 (B) into a scalable sodium-ion electrode
The intermittent nature of renewable energies requires highly reliable grid-level energy storage approaches. A critical consideration in developing this technology is the areal capacity which determines battery performance and influences the cost of battery technology. Of related importance is finding new ways of developing scalable electrodes. In recent years, three-dimensional (3D) printing of conductive scaffolds has emerged as an alternative to overcome the scalability limitations of commercial tape cast electrodes. The research carried out in the current study demonstrates a successful scalability pathway for nanoscale VO 2 (B), a desirable cathode for sodium-ion batteries which has a nano-flower morphology with a crystallite size < 20 nm. By electrodepositing VO 2 (B) onto a graphene aerogel scaffold, we were able to achieve mass loading of over 100 mg·cm −2 and still possess an areal capacity of 10 mAh·cm −2 at a current density of 5 mA·cm −2 . Moreover, after 1000 cycles, these electrodes retained 75% to 80% of their initial capacity. Even at high loading levels, the electrodeposited VO 2 (B) exhibits pseudocapacitive material signatures such as a box-like voltammetry response, linear galvanostatic response, and no phase change upon lithiation. The scalability of the VO 2 (B) electrode is demonstrated in a series of experiments which show the areal capacity to scale upon increase in both mass loading and electrode thickness, with only small changes in specific capacity. Furthermore, this study establishes that nanoscale materials can be scaled up to achieve thick electrodes without compromising their electrochemical properties.
A fluorinated cation introduces new interphasial chemistries to enable high-voltage lithium metal batteries
Abstract Fluorides have been identified as a key ingredient in interphases supporting aggressive battery chemistries. While the precursor for these fluorides must be pre-stored in electrolyte components and only delivered at extreme potentials, the chemical source of fluorine so far has been confined to either negatively-charge anions or fluorinated molecules, whose presence in the inner-Helmholtz layer of electrodes, and consequently their contribution to the interphasial chemistry, is restricted. To pre-store fluorine source on positive-charged species, here we show a cation that carries fluorine in its structure is synthesized and its contribution to interphasial chemistry is explored for the very first time. An electrolyte carrying fluorine in both cation and anion brings unprecedented interphasial chemistries that translate into superior battery performance of a lithium-metal battery, including high Coulombic efficiency of up to 99.98%, and Li 0 -dendrite prevention for 900 hours. The significance of this fluorinated cation undoubtedly extends to other advanced battery systems beyond lithium, all of which universally require kinetic protection of highly fluorinated interphases.
Lithium loss, resistance growth, electrode expansion, gas evolution, and Li plating: Analyzing performance and failure of commercial large-format NMC-Gr lithium-ion pouch cells
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High-Energy Lateral Mapping (HELM) Studies of Inhomogeneity and Failure Mechanisms in NMC622/Li Pouch Cells
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A High-Performance Na-Al Battery Based on Reversible NaAlCl4 Catholyte
This work demonstrates a high-capacity and safe Na-Al battery pairing sodium metal anode and reversible NaAlCl4 catholyte for grid scale energy storage applications. The energy-rich sodium anode allows the full play of the aluminum cathode, resulting in a full-cell capacity of 308 mAh/g at a discharge voltage of 1.6 V. Benefiting from the use of ??-alumina solid electrolyte (BASE), molten sodium anode and reversible Al deposition/stripping from NaAlCl4 catholyte, the battery presents a stable Coulombic efficiency of 100% and energy efficiency of ~95%. At a rate of C/3 (6.77 mA/cm2), the cell maintains 282 mAh/g (447 Wh/kg) after 200 cycles with an excellent capacity retention of 97.6%. Moreover, we elucidate pathways to build sodium-anode-free cells from the discharged state under dry air, which further extends the feasibility of this battery for stationary storage applications. These findings are expected to provide a new platform for the development of practical Al batteries.
Energy and Power Evolution Over the Lifetime of a Battery
Li-ion batteries currently are dominant energy storage devices for electric vehicles. Rechargeable batteries with lower cost, longer lifetime, and higher safety are desired in support of building of a green grid infrastructure. The continued investment in new battery materials, novel battery structures, advanced manufacturing processes, and accelerated testing/validation of battery performance has led to significant progress in battery development and deployment. Battery safety/reliability, which is essential to the success of a battery technology in the real world, naturally becomes the next big topic in battery research. Recently, the increasing interest in long-duration storage, fast charging, battery secondary use, and material recycling to build a circular industry and sustainable material supply chain has compelled further attention to understand the energy/power evolution and safety over the lifetime of a battery. Here, in this short Viewpoint, we discuss some high-level analyses on the energy/power evolution of rechargeable batteries over their life cycles aiming to inspire more discussion on the safety and sustainability of some representative and emerging battery technologies.
Revealing Solvent-Assisted Li+ Transport in the Solid Electrolyte Interphase operando
The performance of energy-dense lithium metal batteries is critically influenced by the properties of the solid electrolyte interphase (SEI). Yet, progress in understanding this layer has been limited by the lack of accurate operando characterization because the SEI evolves dynamically during cycling. Here, we apply dynamic electrochemical impedance spectroscopy (dEIS) to resolve the real-time evolution of the SEI on lithium metal in ether-based electrolytes with varying degrees of fluorination. We find that faster stabilization of the compact SEI resistance correlates with improved passivation and higher Coulombic efficiency. Unexpectedly, compact SEI resistance correlates directly with Li+ solvation energy, revealing that weaker Li+ solvation increases not only bulk but also interphase resistance. These findings challenge the conventional view of the SEI as a purely solid-phase conductor and instead support a solvent-assisted Li+ transport mechanism within the compact SEI. This framework emphasizes the need to balance SEI ionic conductivity with the Li+ solvation environment to maximize lithium metal battery performance.
Battery Electrolyte Design for Electric Vertical Takeoff and Landing (eVTOL) Platforms
Here, the development of robust and high-performance battery systems is crucial for the advancement of Electric Vertical Takeoff and Landing (eVTOL) vehicles for urban air mobility. This study evaluates the performance of different lithium-ion battery chemistries under Electric Vertical Takeoff and Landing (eVTOL) load profiles. The actual flight data coupled with physical models is used to create discharge profiles for testing on developed lithium-ion cells for eVTOLs. The performance of a standard liquid electrolyte (1.2 M LiPF 6 in EC:EMC), labeled Gen-2, is benchmarked and compared with a fast-charging electrolyte (1.2 M LiFSI in EC:EMC), labeled XFC. Cell analysis involves the use of various techniques, such as impedance spectroscopy, polarization curves, and capacity retention measurements. Capacity retention is stable for both systems over 500 cycles, but unique discharge capacity trends are observed for different mission segments. During the initial takeoff hover stages, Gen-2 electrolytes experience substantial voltage fade, while XFC electrolytes maintain consistent behavior. In general, the Gen-2 electrolyte demonstrated lower discharge overpotentials and higher decay during cycling compared to the XFC electrolyte. This work highlights the complexity of eVTOL battery behavior and provides insights into battery system design, contributing to the advancement of battery energy storage solutions for urban air mobility.
Nanostructured Powders Made from Flame Spray Pyrolysis for Li-Ion Cathode
Flame processes are the most economic ones to produce fine powders and have been used to produce pigment titanium oxide and fused silica in large volumes. In this work a flame spray pyrolysis (FSP) process is used to make positive electrode materials for Li-ion battery, which is made of complex metal oxide powders, such as Li(Ni1/3Mn1/3Co1/3)O2. In particular, the work was focused on making the NMC materials with stoichiometric compositions and desired morphologies. During the pyrolysis process different morphologies can be formed, involving often powders with primary nanoparticles. Such nanostructures were found to have affected the battery performance. Detailed results of the synthesis, characterization, and battery testing of the NMC powder materials will be presented.
Insight of Synthesis of Single Crystal Ni-Rich LiNi 1-x-y Co x Mn y O 2 Cathodes
Single-crystal Ni-rich LiNi 1-x-y Co x Mn y O 2 (NCM) cathodes have garnered widespread attention in the lithium-ion battery community due to their unique advantages in mechanical performance and their ability to minimize interfacial electrochemical side reactions. The synthesis of single-crystal materials with monodisperse and appropriate size, minimal lattice defects, and highly ordered structures is the key for high-performance batteries. However, achieving this goal poses challenges due to the lack of in-depth understanding regarding specific experimental parameters and the solid reaction mechanism during the synthesis process. Further, in this review, the aim is to provide an in-depth analysis of the critical process parameters involved in the synthesis and their impact on crystal morphology, structure, and electrochemical performance. Consequently, the first section focuses on the effect of the precursor morphology, lithium salt, atmosphere, and sintering procedure. In the second section, the study delves into an in-depth discussion of the solid reaction and crystal growth mechanism. Lastly, it is concluded by highlighting the prospects and challenges associated with the synthesis and application of single-crystal Ni-rich NCM cathodes.
Vacancy‐Enabled O3 Phase Stabilization for Manganese‐Rich Layered Sodium Cathodes
Abstract Manganese‐rich layered oxide materials hold great potential as low‐cost and high‐capacity cathodes for Na‐ion batteries. However, they usually form a P2 phase and suffer from fast capacity fade. In this work, an O3 phase sodium cathode has been developed out of a Li and Mn‐rich layered material by leveraging the creation of transition metal (TM) and oxygen vacancies and the electrochemical exchange of Na and Li. The Mn‐rich layered cathode material remains primarily O3 phase during sodiation/desodiation and can have a full sodiation capacity of ca. 220 mAh g −1 . It delivers ca. 160 mAh g −1 specific capacity between 2–3.8 V with >86 % retention over 250 cycles. The TM and oxygen vacancies pre‐formed in the sodiated material enables a reversible migration of TMs from the TM layer to the tetrahedral sites in the Na layer upon de‐sodiation and sodiation. The migration creates metastable states, leading to increased kinetic barrier that prohibits a complete O3‐P3 phase transition.
Modeling High Current Pulsed Discharge in AA Battery Cathodes: The Effect of Localized Charging during Rest
During high current operation, substantial heterogeneity develops within battery cathodes, particularly when their thickness is large. Heterogeneity relaxation during subsequent rest is important for understanding battery performance under pulsed conditions. Localized charge balancing phenomena within batteries at zero net current are not well understood and merit investigation. In this work, the heterogeneity within cathodes of commercial alkaline Zn–MnO 2 batteries is measured during discharge and monitored during rest using energy dispersive X-ray diffraction (EDXRD). Significant gradients in protonation form during discharge and partially relax under rest. It is demonstrated that the proton gradient relaxation is through local redox activity at zero net current, where local (de)protonation works to redistribute charge across the cathode thickness. To support this redox-based relaxation, a fundamental kinetic study on prismatic MnO 2 cathodes is conducted to determine an appropriate model to describe both discharge and charge kinetics of MnO 2 . These kinetics are incorporated into a computational model to simulate the proton gradient formation and partial relaxation under identical discharge conditions as the operando EDXRD experiments. Model and experimental data are found to be in excellent agreement, correctly predicting localized charge balancing at rest.
Shorting at Long Duration: Impact of Extended Discharge Capacity on Battery Solid Electrolytes
Long-duration energy storage (LDES) is critical to a stable, resilient, and decarbonized electric grid. While batteries are emerging as important LDES devices, extended, high-power discharges necessary for cost-competitive LDES present new materials challenges. Here, focusing on a new generation of low-temperature molten sodium batteries, we explore here unique phenomena related to long-duration discharge through a well-known solid electrolyte, NaSICON. Specifically, molten sodium symmetric cells at 110°C were cycled at 0.1 A cm -2 for 1-23 h discharges. Longer discharges led to unstable overpotentials, reduced resistances, and decreased electrolyte strength, caused by massive sodium penetration not observed in shorter duration discharges. Scanning electron microscopy informed mechanisms of sodium penetration and even “healing” during shorter-duration cycling. Importantly, these findings show that traditional, low-capacity, shorter-duration tests may not sufficiently inform fundamental materials phenomena that will impact LDES battery performance. This case highlights the importance that candidate LDES batteries be tested under pertinent long-duration conditions.
Rational solvent molecule tuning for high-performance lithium metal battery electrolytes
Electrolyte engineering improved cycling of Li metal batteries and anode-free cells at low current densities; however, high-rate capability and tuning of ionic conduction in electrolytes are desirable yet less-studied. In this study, we design and synthesize a family of fluorinated-1,2-diethoxyethanes as electrolyte solvents. The position and amount of F atoms functionalized on 1,2-diethoxyethane were found to greatly affect electrolyte performance. Partially fluorinated, locally polar –CHF 2 is identified as the optimal group rather than fully fluorinated –CF 3 in common designs. Paired with 1.2 M lithium bis(fluorosulfonyl)imide, these developed single-salt-single-solvent electrolytes simultaneously enable high conductivity, low and stable overpotential, >99.5% Li||Cu half-cell efficiency (up to 99.9%, ±0.1% fluctuation) and fast activation (Li efficiency >99.3% within two cycles). Combined with high-voltage stability, these electrolytes achieve roughly 270 cycles in 50-μm-thin Li||high-loading-NMC811 full batteries and >140 cycles in fast-cycling Cu||microparticle-LiFePO 4 industrial pouch cells under realistic testing conditions. The correlation of Li + –solvent coordination, solvation environments and battery performance is investigated to understand structure–property relationships.